Abstract: XRD, TEM, SEM and tension testing were used to investigate the microstructure evolution and mechanical hardening of 18-18-0.5N high-nitrogen austenitic stainless steel during cold rolling. The experimental results show that there is no sign of deformation-induced phase transformation. A inflection point of microstructure and mechanical properties was found at 43.8% reduction. An excellent predicting equation of yield strength to strain was presented.