Abstract: Three-dimensional temper rolling processes are simulated by nonlinear elastoplastic finite element software called ABAQUS. In this simulation, the initial flatness defects of steel strips are modeled by the temperature field, and the adjustment effect of flatness control methods on the support roll gap shape is comprehensively expressed by the contour change of rigid work rolls. Based on the above mechanical model, flatness defects after temper roiling and their dependency on initial flatness defects and temper rolling conditions are numerically studied for steel strips with initial flatness defects, and moreover, the heredity and evolution laws of flatness defects in the temper rolling process are presented. Simulation results show that the support roll gap shape is the most important factor deciding the heredity and evolution of flatness defects, and the initial flatness defect level of entry strips has some effect on the flatness of exported strips.