Abstract: Cyclic quenching process is currently one of the effective methods to improve the heredity characteristics of steel structure. It not only refines grain size but also enhances the strength and hardness of metal materials. In this experiment, 40Cr steel was taken as the object, and multiple cycles of quenching process were compared with a single quenching process to explore the effect of cycle quenching times on the metallographic structure and hardness of 40Cr steel. The effect of holding time during tempering process after cyclic quenching on microstructure and hardness was also examined. The results showed that at 830 ℃, with a holding time of 20 minutes, three cycles of quenching achieved optimal grain refinement effect. Compared with a single quenching, three cycles increased hardness by 5%, significantly enhancing material strength and hardness. Furthermore, when tempering was performed after cyclic quenching, the hardness slightly decreased with prolonged holding time.