Physics InstitutePhD student in Sciences Study of heavy-ion-induced fusion-fission reactions is important for understanding the physics of nuclear matter and nuclear models. In this work, we study the mechanism of nuclear reactions of 11 B + 181 T a, 11 B + 197 Au, 11 B + 209 Bi and 7 Li + 208 P b at intermediate energy using CRISP model and also analyze the nuclear reaction processes starting from the initial nucleus-nucleus collision up to the fragments production. The experimental data are measured at the LNR Phasotron (JINR, Dubna, Russia) and also taken from Ref. [1]. The fission process is studied using multimodal fission model for 7 Li + 208 P b