Abstract: Aiming at the problem that the mechanical properties of 30CrMnSiA steel hooks after isothermal quenching are not up to the standards, the influence of isothermal temperature on the metallographic structure and mechanical properties of the material was analyzed by process tests. The results show that the optimum isothermal quenching temperature of 30CrMnSiA steel hooks is 340～360℃. After isothermal quenching, the complex phase structure of bainite and martensite can be obtained. With the increase of isothermal temperature, the content of upper bainite increases gradually, and the hardness and strength values decrease, Simultaneously maintaining good elongation and cross-sectional shrinkage.