Abstract: The scuffing mechanism of piston ring cylinder liner is introduced. The main factors that influence the piston ring scuffing are summarized as running in, surface roughness, contour of ring, thermal and mechanical deformation of piston assembly, lubricant, material, and surface protective layer. The intensified coefficient p e v m is suggested as the criterion for judging scuffing degree. The possibility of scuffing occurrence is divided into four grades according to the values of p e v m. The tribological design measure to avoid scuffing of pistion ring cylinder liner is reviewed.