He was awarded scholarship for studying Library Science in the University of Columbia, USA from where he obtained M S with distinction in the year 1955. Prof. Husain was the first person in the whole of erstwhile Pakistan in obtaining the said degree. On return from the USA he was appointed. Librarian of the East Pakistan Central Public Library. He started a new challenging professional carrier as the first librarian of EPCPL. He submitted a plan for a separate building for Central Public Library foundation of which was made in the year 1958 at Shahbagh beside the National Museum. In 1962 Prof. Husain was appointed Officer on Special Duty for Library Development in the Directorate of Education. He placed before the then Government a development scheme for establishing libraries in four divisional headquarters of the province. The scheme given by him was implemented in phases. His next scheme was to establish public libraries at district level and as a consequence of which public library started functioning in many districts. He also proposed plan for establishing public library at thana level for greater interest of teachers, students and users which the government accepted on principle to implement phase by phase.

The librarians of government colleges were given the status of second class gazetted officer. By the sole effort of Prof. Husain the librarians of governments colleges having Masters Degree were upgraded to the status of first class gazetted officer. His another plan for upgrading the librarians of the government colleges was to make open chance for promotion to next higher post according to their merit. Though the plan has not been implemented but Bangladesh Library Association has been trying its utmost to materialise it.

In 1978 the then government formed a committee headed by late Professor Abul Fazal, Advisor of Education as Convener and Prof. Ahmad Husain as its Member-Secretary. The committee submitted a project profile to the President and appraised him about dire necessity of a national library for which they appealed for placing a bill in the parliament. Ultimately the national library and archives came into being.

Prof. Husain was entrusted with the responsibility of preparing a plan for establishing an Islamic University in the country. In due course he submitted the project profile for establishment of the University in Kushtia, the north-western part of the country deprived from various opportunities.

After retirement from government service Prof. Husain was appointed Director, Islamic Academy (now Islamic Foundation, Bangladesh) in 1969. At that time the academy was in extreme financial crisis. It was not possible to provide financial support from the yearly budget allocation for research works and publishing books, periodicals. He took a firm decision to carry on research work with the fund allocated for procurement of vehicle for the academy. As a result during his tenure as Director of the academy translation of the Holy Quran into Bengali was completed. With a view to generating income for the academy Prof. Husain proposed to the government to give the shops of the Baitul Mukarram Mosque under Academy's management control. After the expiry of his service in the Foundation the government appointed Prof. Husain as the Member of the Governing Body of Islamic Foundation for several terms. He was a member of the editorial board of Islamic Encyclopedia Project and performed the job till his death.

Professor Ahmad Husain was a good organiser. He was elected Vice-President of Salimullah Hall Union perhaps in the year 1930 or 1931. When he was studying in USA he took leading role in forming Pakistan Students' Association there and prepared a draft constitution. For indomitable spirit of Prof M S Khan and Prof. Ahmad Husain the two pioneers of library movement Diploma course in Library Science was started in Dhaka University. Later on Dhaka University introduced both Honours and Masters Degree in Library Science. Due to their dauntless efforts some other varsities of the country introduced Honours and Masters course in Library Science. Prof. Husain was associated with Bangladesh Library Association (BLA) as its President for more than one term. Prof. Husain also took leading part in the formation of Chittagong Samity, Dhaka since its inception. He was elected General-Secretary of Chittagong Samity twice. He was given a crest in 1999 posthumously in recognition for sincere service to the Samity.

Professor Husain worked as the Editor and member of the editorial board of the Library News, a journal regularly published by Bangladesh Library Association. He enjoyed the credit of editing many textbooks in connection to library science and religious education. His writings on library development were published both at home and abroad.

Educationist Husain on various occasions worked as one of the members of national curriculum committee, chief examiner and tabulator. He performed the responsibility as an adviser of Asia Foundation. The libraries of Dhaka, Chittagong and Rajshahi Universities were renovated by virtue of his expert opinion.

Prof. Husain earned reputation as an honest and punctual man. He was known for his indomitable spirit and unflinching moral courage. He had the opportunity of coming in contact with great personalities like Shre-e-Bangla A K Fazlul Haque, Husain Shahid Suhrawardy, Moulana Abdul Hamid Khan Bhashani, Bangabandhu Sheikh Mujibur Rahman, Moulana Akram Khan, Dr Mohammad Shahidullah, Dr Kazi Motahar Husain, Abul Hashim, Prof. Abul Fazal, Dr Zakir Husain, Moulana Abdur Rashid Tarkabagish, Principal Dewan Mohammad Azraf.

In the year 1974 Moulana Abdul Hamid Khan Bhashani called a conference at Santosh inviting the leading educationists, intellectuals, politicians and social workers in order to take ideas from them for founding an Islamic University. In this conference Prof. Husain was specially invited by the Moulana who accepted many of his proposals and conceptions. Prof. Husain represented his country in many international seminars on library development. Professor Ahmad Husain breathed his last at the age of eighty-nine on 31st August, 1996.