A new method for post-treatment of PS(porous silicon), sulfur passivation by microwave plasma assistance in vacuum,is reported in this paper.Fourier transform infrared spectrum indicated that the treated sample surface is mainly covered by SiSx and SiOy.Compared with the as etched PS,the photoluminescence (PL) intensity of the sample is 3.5 times stronger,and the 4nm blueshift of the PL peak was observed experimentally;furthermore,the intensity decay of the PL peak hasnot been observed after 60d in the atmosphere.Therefore,sulfur passivation is an effective post treatment for enhancing PL intensity and stabilization of PS.