The paper aims to explore the influences of lapping parameters on the surface roughness and residual stress of the workpiece before and after carburizing of 18CrNiMo7-6 steel to provide a basis for reducing the surface roughness of the workpiece and improve the surface quality. The surface roughness and residual stress of the workpiece before and after lapping were detected by three-dimensional surface profiler and X-ray residual stress analyzer. The influential rules of lapping parameters such as particle size, lapping pressure, lapping speed and lapping time on the surface roughness and residual stress of the workpiece were studied by single factor test. With the particle size of the lapping pad increasing from 400# to 3000#, the surface roughness value of the workpiece before and after carburizing decreased, reaching Ra 15~17 nm. The surface residual stress value of the workpiece increased before and after carburizing. The residual pressure stress rose to the residual tensile stress after carburizing. When the particle size of the lapping pad was 400#, the residual stress of the workpiece before and after carburizing was –506.54 MPa and –587.29 MPa respectively. When the particle size of the lapping pad was 800#, with the increase of lapping pressure, lapping speed and lapping time, the surface roughness value of the workpiece before and after carburizing was reduced, and the surface residual compressive stress value increased. Under the same lapping conditions, the surface roughness value of the workpiece after carburizing is generally smaller than that of the substrate, and the residual stress value of the carburized surface is generally larger than that of the substrate surface. The hardness and wear resistance of 18CrNiMo7-6 steel after carburizing are greatly improved, and the weakening of plastic deformation during lapping is an important cause of the above phenomenon.