Vapor etching was used to etch diamond wire sawn multicrystalline silicon wafers. The vapor was produced from 2 g silicon wafer adding into HF-HNO3-H2O acid mixture solution (400 mL, in the volume ratio of 6: 3: 1) to reaction at room temperature. Diamond wire sawn multicrystalline silicon wafers were etched in vapor. Etching for 4 min, saw marks can be removed and honeycomb etched pits were densely covered with silicon wafer surface. The reflectivity of silicon wafer decreases remarkablely by using the vapor etching methods. The reflectivity of the silicon wafers by vapor etching is low to 19.51%. The micro-roughness of diamond wire sawn mulicrystalline silicon wafers etched with vapor method is actually about 20% higher than that of etching with traditional acid mixture solution method.