Abstract: Dynamic continuous cooling transformation (CCT) curves of DP600 steel were determined on Gleeble-3800 thermal simulator. The hot rolled process were simulated to study the effect of rolling parameters on microstructure, and to optimize rolling parameters. The results show that there were self-exist ferrite region and bainite region on CCT curves, and broader steady austenite region existed in the region above-mentioned. The effect of the rolling parameters on the microstructure was obvious, and the best microstructure was obtained when the tested steel was cooled from 750 ℃ to 710 ℃ at a cooling rate of 1 ℃·s-1, and then cooled quickly to 600 ℃ to coil after end-rolling at 850 ℃.