By analysizing the theory of laser cutter,a rapid laser cutter method is given for cutting thick silicon wafer.Considering laser medium thermal lens effect and thermal focal length changing with the pumping power,using plano-convex high reflectivity mirror as the back cavity mirror to compensate the heat lens influence,utilizing the Nd∶YAG self-aperture effect also,more than 50 W average power 1.064 μm laser output is obtained with beam quality factor M² of 4.19.Choosing suitable beam expander factor,appropriate aperture diameter of exit beam and repetition rate,when the cutting velocity is 400 mm/min,a silicon wafer of 0.75 mm thickness can be penetrated;when the cutting velocity is 100 mm/min,a silicon wafer of double-layer 0.75 mm thickness can be penetrated.Experimental results show that the cross section is fine in narrow groove and excellent repeatability precision,it is more better than that of other conventional cutting methods.