Vapor Etching (VE) was used to etch diamond wire sawn mc-silicon wafers. The vapor was generated from heating the acid mixture solution of HF-HNO3 in the volume ratio of 1: 3 (the total volume of the solution is 400 mL) at 90 ℃. The results showed that etching for 15 minutes, saw marks can be removed and lots of small corrosion pits which appeared in big corrosion pits were densely covered with silicon wafer surface, the average size of the corrosion pits was about 1 μ m, while that by wet acid etch was over 10 μ m. The wafer surface roughness with VE method is actually 3 times higher than that with traditional wet acid etching method. The effect of VE is obvious and the reflectivity is low to 12.11%.