Abstract: By means of Surface Nano-Crystallization (SNC), a nanostructured surface layer was formed on 316L stainless steel plate, with the grain refined into nanoscale. The grain sizes are about 12nm at the top surface layer, and gradually increase with the depth. Mechanical properties of nanostructured surface layer are analyzed using nanoinedtation. The results show that the nanohardness and the elastic modulus of the nanostructure surface layers are about 6.05GPa and 227GPa respectively, and are 1.4 times and 1.2 times of those of the matrix. The nanohardness and the elastic modulus decrease with the depth, and then trend to stable values. The hardening index of nanostructure surface layers is about 0.44, 1.5 times of the value of the matrix.