Sushil Modi was born on 5 January 1952 in a Marwari (Vaishya Bania) family. His father was Moti Lal Modi and his mother was Ratna Devi. He has done BSc from B N College, Patna. He graduated Patna Science College and did Botany Hons in 1973. Later he left MSc Botany Course in Patna University, to join social movement started by Jai Prakash Narayan.