In this paper, according to the requirements of SEMI standard for 12-inch wafer marking, the 1066 nm fiber laser wafer marking system was used to study the laser marking process of the bare silicon wafer and the coated wafer. The power percentage of the laser was changed by the control variable method. Dot-style SEMI fonts were marked on the wafers, and the quality and readability of the marks were evaluated. The study found that the laser power range corresponding to the bare silicon wafer mark from scratch to severe sputtering is 11.77~19.25 W, and the power range corresponding to the coated silicon wafer is 4.40~11.77 W. The Dot morphology is more in line with the SEMI standard requirements. The melting threshold of the coated wafer become smaller, but the processing window become narrower, the roundness of the marking characters and barcode Dot are poor, and the spatter is not easy to control. The OCR reading rates of the two wafers are basically same.