The structure of surface layer of monocrystalline Si by implanting nitrogen cluster ions N+10 was transformed directly the nanocrystalline, which led to the change in optical properties of monocrystalline Si. Excited by the ultraviolet light of 250—320nm, the sample showed a clear luminescence band of 330—500nm and an extra intensive spectral peak with good monochromaticity around 360nm. The intensity of the peak were 5 times high as the intensity of the substrate or N+ implantation samples and 1.5 times high at the N+2 implantation samples, respectively. It was also found there were two other stable luminescence bands around 730nm in the visible region and around 830nm in the infrared region, respectively. The preliminary study indicated that an excellent photoluminescence material was formed in the implanted layer.