Abstract: Using non quenched and tempered steel materials to replaced quenched and tempered steel materials to manufacture engine expanding and breaking connecting rods could save a heat treatment process, which was conducive to energy conservation and environmental protection. Using expanding and breaking technology to replaced traditional flat cutting technology was conducive to improving the assembly accuracy of connecting rods. The chemical composition, macrostructure, microstructure and non-metallic inclusion of KNF33MAM non quenched and tempered steel for expanding and breaking connecting rod were analyzed. The results could lay a theoretical foundation for improving the domestic material level.