Abstract: The Siface and C face of 6H-SiC single crystal wafer were lapped by using the copper based lapping pad with spiral grooves and the effects of lapping pressure,pad speed and abrasive size on the material removal rate and the surface roughness of SiC were studied. The results show that the lapping characteristics of C face and Siface have obvious difference. The C face is easier to lap and the material removal rate of C face is larger than that of the Siface. The lapping pressure is a key parameter that influences material removal rate and surface roughness. The higher the lapping pressure is,the larger the material removal rate is,but the surface roughness R_a increases as well. High lapping pressure can generate scratches on SiC surface. To achieve a better surface roughness,the lapping speed of the C face should be faster than that of the Siface. It's also found that agglomeration of the diamond abrasives will seriously affect the quality of the lapped surface. Therefore,the lapping quality of SiC surface with 3 μm diamond abrasive is better than that with 1 μm diamond abrasive. After lapping for 5 min with 3 μm diamond abrasive,the surface roughness of Siface decreases from original R_a 130 nm to R_a 5.20 nm,and the surface roughness of the C face decreases to R_a 5.49 nm.