Abstract: The decarbonization of spring steel at different cooling rates and the influence of cooling rate on the properties of spring steel were studied by optical microscope, and the mechanism of decarbonization production was analyzed. The results show that, with the increase of cooling rate, the diffusion capacity of C decreases, and it can inhibit the total decarburization of the sample surface and slow down the ferrite precipitation, reduce the generation of total decarbonization. At the same time,with the increase of the cooling rate, the residence time of the specimen in the two-phase region decreases, the decrease of the first eutectoid ferrite results in the increase of tensile strength of spring steel and the decrease of section shrinkage.