This study is to investigate the effect of thermo mechanical treatment on the mechanical properties of 316L stainless steel. ${alpha}^{prime}$ and ${varepsilon}$-martensite was formed by deformation. With increasing number of thermo mechanical treatment, volume fraction of martensite was increased rapidly, and then unchanged. With increasing number of thermo mechanical treatment, hardness and strength was increased rapidly, and then unchanged while elongation was decreased rapidly, and then unchanged. With increasing volume fraction of martensite formed by thermo mechanical treatment, hardness and strength was increased rapidly, elongation was decreased rapidly. Thus, hardness, strength and elongation of thermo mechanical treated 316L stainless steel was strongly affected by martensite formed by thermo mechanical treatment. Good combination of strength and elongation was obtained from thermomechanical treatment.