Abstract: Cr4Mo4V quenched and tempered steel balls with mixed crystal structure were treated with subcritical annealing and isothermal annealing respectively, and then the grain improvement was observed after quenching at 1115 ℃.The micro distortion of Cr4Mo4V samples in different states was analyzed by X-ray diffraction. The morphology and distribution of secondary carbides in each sample were compared and analyzed by light microscope and scanning electron microscope. The results show that the mixed grain structure of Cr4Mo4V steel ball is improved, but the grain is still coarse.Intermediate annealing does not effectively eliminate the genetic phenomenon of quenching coarse grain. There are indications that the inheritance of coarse grains is closely related to the directional distribution of quenched insoluble carbides and secondary carbides in the microstructure before re-quenching.