Abstract: The effects of heat treatment on the fatigue life and corrosion resistance of 304/45 steel composite bars were studied by flexural fatigue test and electrochemical experiment. The results show that the diffusion of carbon in the hot-rolled state is mainly concentrated at the grain boundary, resulting in intergranular sensitization. After solution treatment, the deformation strengthening effect is eliminated and the fatigue performance is reduced. The carbides in stainless steel are dissolved and then ratained into the grains of austenite. After aging treatment, the carbon elements in the austenite grains form chromium-rich carbides, which can be uniformly precipitated within the grain boundary grains. The corrosion resistance has decreased, but the resulting dispersion strengthening has increased the hardness and strength of the composite bar, and the fatigue strength has been greatly increased.