In order to explore the suspected rust problem of local position on the surface of 38MnVS6Ti hypoeutectoid low alloy steel piston, the metallographic structure, microhardness, surface morphology and energy spectrum of the suspected rusted piston were comprehensively tested and analyzed. The results show that there is ledeburite structure on the surface of the local rust position of the piston. Through a comprehensive analysis of the manufacturing process and process of steel pistons, it is found that the high-carbon release agent sprays on the surface of the mold during the original forging process entered the molten iron after the partial high-temperature surface oxide of the blank melted, forming a high-carbon molten iron. The high-carbon molten iron undergoes eutectic reaction during the forging process of the blank to form a high-temperature ledeburite structure. The high-temperature ledeburite forms a room-temperature ledeburite after the forging blank is cooled at a controlled temperature. By reducing the forging temperature and diluting the release agent, the surface temperature and surface carbon content of the piston blank can be reduced, thereby blocking the formation conditions of the ledeburite on the local surface of the steel piston and eliminating the ledeburite structure. The optimized piston forging process has been verified by actual production. The verification results show that the improved forging process can solve the local rust problem of steel piston caused by ledeburite.