Abstract: In view of the brittle fracture failure of the end of ball screw caused by insufficient material toughness, this paper carries out the improvement research of martensitic precipitation hardening stainless steel 1Cr14Co14Mo5. Based on the local composition adjustment of 1Cr14Co14Mo5, the study adjusts the original solid solution + aging heat treatment process, that is, the microscopic mechanism of the austenite grains is refined by cyclic phase transformation treatment, to obtain a refined lath martensite structure, and thus to enhance the plasticity and toughness of the material. The microstructure and performance results show that increasing the solution temperature from 1000℃ to 1100℃ can effectively improve the impact toughness of 1Cr14Co14Mo5. 3~4 times of cycle phase transformation treatment can refine the grains and the average grain size is less than 10μm, which can improve the impact toughness KU2 of the material from 20.2 J to more than 60 J and can slightly increase the fracture toughness K1C value.