Abstract: In order to solve the problem of grain growth for the Mn18Cr18N retaining ring steel during the multi-heating hot forging process,the effect of heating condition on grain size was investigated.The two-heating forging test had also been verified with small samples.The results show that the grain size of forgings had a certain hereditary,and the grain size didn′t dramatically grow when the forging reheated at 1 100℃ for less than 5 h or 1 050℃ for longer time.And the grain growth mode of the steel was D5.9t-D5.90=2.2×1026exp-486 809强激光与粒子束RT·t.