Abstract: 55CrSi wire rod is widely used in the manufacturing of piston rings of automobile engines. In the process of production, it is easy to have uneven hardness of wire section. The effects of heat treatment process on the uniformity of microstructure and properties of the wire rod were studied. The structure, composition and properties of the material were tested by scanning electron microscope, metallographic microscope, energy spectrometer and Vickers hardness tester. The experimental results show that the austenitizing state during heat treatment has an important influence on the subsequent microstructure and properties. When the austenitizing temperature is low or the time is short, a large white block appears in the metallographic structure, which is a soft phase, resulting in low hardness. When the degree of austenitization is high, the size of white block in metallographic structure is small, and the uniformity of structure and properties is improved. When the austenitizing process is not sufficient, it is found that the carbon distribution of the material is uneven by EDS detection, the carbon content in the low hardness zone is low, about 0.2%, and the carbon content in the high hardness zone is high, about 0.43%. The high degree of austenitization is conducive to the uniformity of carbon element distribution and the uniformity of properties after quenching and tempering.