Abstract: To investigate the effects of different cooling methods on the tempered microstructure and tensile properties of 1Cr13Ni steel, four cooling processes—water quenching + tempering, oil quenching + tempering, air cooling + tempering, and furnace cooling + tempering—were applied. The results show that the as-quenched microstructure mainly consists of martensite and retained austenite, while the tempered microstructure is primarily composed of sorbite and ferrite. Faster cooling rates led to a higher proportion of martensite. Subsequent tempering of the rapidly cooled samples revealed polygonal and fine ferrite grains, along with partial dissolution of cementite. Both the as-quenched and tempered hardness increased significantly. Among the processes, water quenching + tempering yielded the best tensile properties, with a strength of 1191 MPa and an elongation of 24.24%. This indicates that the martensite content directly influences the mechanical properties of 1Cr13Ni steel. Furthermore, a slower tempering rate resulted in reduced grain boundary density and dissolution of carbides, which contributed to improved material plasticity.