Abstract: The test and characterization method of work hardening index n value of bar and wire on common testing machine was designed. The influencing factors of work hardening of SWRCH6A-10A series cold forging steels were obtained, and the correlation between chemical composition, mechanical properties, microstructure and n value was studied. The reasonable control indexes of n value were studied. The results could guide the design and optimization of the production process, so that each tester could obtain the work hardening index of the material on any tensile testing machine.