SiNWs (silicon nanowires) are prepared by metal Ag assisted chemical etching (MACE) method by controlling the concentration of H2O2 in the etching solution, the etching solution temperature and the etching time, and the preparation parameters are optimized. The results of scanning electron microscopy (SEM) show that the SiNWs are the most uniform and regular, and the photoluminescence (PL) intensity is better when the concentration of H2O2 in the etching solution is 0.5M and the temperature of the etching solution is 25oC. With the increase of etching time, the length of SiNWs and surface oxides increase linearly, and the diameter of nanowires is about 100nm. The orange-red PL spectrum is believed to be caused by the quantum confinement effect of silicon nanocrystals. With the increase of etching time, the primary and secondary luminescence peaks at 633nm and 699nm are blue shifted. The SiNWs obtained by the sample etched for 4 min has a moderate structure and length, and its luminescence intensity is the highest, which is an order of magnitude higher than that of the sample etched for 12 min. SiNWs prepared by this method has important application potential in the fabrication of silicon nanostructured based optoelectronic devices.