Maitra rose to prominence as a student activist and was elected as the General Secretary of the Students' Federation of India (SFI), the student wing of the CPI(M). Following his tenure with the SFI, he became the Secretary of the Democratic Youth Federation of India (DYFI), the youth wing of the party, a position from which he helped organize and mobilize young people across India.
A committed communist, Sunil Maitra eventually became a member of the Central Committee of the CPI(M), the party's highest decision-making body. He was also elected as a member of the West Bengal Legislative Assembly, representing his constituency. Throughout his political career, he was known for his organizational skills, ideological commitment, and ability to connect with grassroots activists.
Sunil Maitra passed away in 1996, leaving behind a legacy as a dedicated leader who contributed significantly to the communist movement in India, particularly in nurturing its student and youth cadres.