Abstract: A self-designed experimental apparatus was employed to study the high temperature solidification phase change process of DP590 steel at the different cooling rate and get the phase-transition temperature from liquid phase (L) to high temperature ferrite phase (δ) then to austenite phase (γ). In addition, the solidification phase transition (SPT) curves of DP590 steel were plotted. Results show that when cooling rate was 0.006 ℃·s-1, the beginning temperature of δ phase transition was between 1 520 ℃ and 1 535 ℃, the finishing temperature of δ phase transition was about 1 490 ℃. As the cooling rate reached to 0.33 ℃·s-1, the beginning temperature of δ phase transition was between 1 510 ℃ and 1 520 ℃, the finishing temperature of δ phase transition was between 1 480 ℃ and 1 490 ℃. The beginning temperature of γ phase transition was above 1 460 ℃, the finishing temperature of γ phase transition was below 1 435 ℃. The phase transition mode changed, the phase diagram moved down, and the temperature interval of phase reaction decreased, with increasing the cooling rate.