The solidification process of AISI 304 stainless steel during cooling at a rate of 0.05 K/s has been observed in situ using a confocal scanning laser microscope(CSLM).The results show that the δ phase appeared first in liquid steel,as the temperature decreased,the γ phase precipitated prior at δ-grain boundary at 1 452.2 ℃,the liquid steel disappeared at 1 431.3 ℃,and then the γ phase precipitated on the δ ferrite.Based on the Scheil-Gulliver solidification model,the solidification processes of AISI 304 stainless steel are simulated using the Scheil model in Thermo-Calc,and the simulation results agree well with the results observed in the experiment. The solidification process of AISI 304 stainless steel during cooling at a rate of 0.05 K / s has been observed in situ using a confocal scanning laser microscope (CSLM). The results show that the δ phase started first in liquid steel, as the temperature decreased , the γ phase precipitated prior at δ-grain boundary at 1 452.2 ° C, the liquid steel disappeared at 1 431.3 ° C, and then the γ phase precipitated on the δ ferrite. Based on the Scheil-Gulliver solidification model, the solidification processes of AISI 304 stainless steel are simulated using the Scheil model in Thermo-Calc, and the simulation results agree well with the results observed in the experiment.