The effect of thermomechanical control processing(TMCP)on microstructure and mechanical properties of Fe-0.2C-1.44Si-1.32Mn hot rolled TRIP steel was investigated through experiments.Strain-induced transformation and transformation-induced plasticity behavior of retained austenite were analyzed.The results show that with multipass deformation,reduction per pass of more than critical deformation in austenite recrystallization region and total reduction of more than 58% in non-recrystallization region and high temperature section of two-phase region,austenite can be refined before γ→α transformation.It is beneficial to obtain refined ferrite grain in final microstructure.To obtain fine and uniform microstructure and excellent strength-ductility balance,a three-stage cooling process(laminar cooling-air cooling-ultra-fast cooling)after hot rolling was conducted.The ultimate tensile strength and elongation of the investigated steel can reach 663 MPa and 41%,respectively. The effect of thermomechanical control processing (TMCP) on microstructure and mechanical properties of Fe-0.2C-1.44Si-1.32Mn hot rolled TRIP steel was investigated through experiments. Strain-induced transformation and transformation-induced plasticity behavior of retained austenite were analyzed. The results show that with multipass deformation, reduction per pass of more than critical deformation in austenite recrystallization region and total reduction of more than 58% in non-recrystallization region and high temperature section of two-phase region, austenite can be refined before γ → α transformation. It is beneficial to obtain refined ferrite grain in final microstructure. To obtain fine and uniform microstructure and excellent strength-ductility balance, a three-stage cooling process (laminar cooling-air cooling-ultra-fast cooling) after hot rolling was conducted. The ultimate tensile strength and elongation of the investigated steel can reach 663 MPa and 41% respectively.