Abstract: Upsetting-stretching deformation of 100 Cr6 steel was carried out, the influence of upsetting-stretching passes on the grain refinement and hardness was studied, and the structure change of the steel after water quenching was analyzed.The results show that the grain size in the center of the sample decreases from 122.1 μm to 24.1 μm, a decrease of 80.3% with the increase of upsetting-stretching passes from one upsetting and one stretching to three upsetting and three stretching. The grain size at the edge of the sample reduces from 93.0 μm to 22.1 μm, decreasing by 76.2%. After heating and quenching, the microstructure of the sample is coarse austenite, and after upsetting-stretching and quenching, the microstructure is quenched acicular martensite +a small amount of agglomerate quenched troostite. The hardness of the center of the sample after upsetting-stretching and quenching is 54.2-56.2 HRC, and the hardness of the edge is 54.8-57.8 HRC.