In this research, sulphurized test pieces were made and the multiasperity sphereshape model of surface contact between sulphurized layer and unsulphurized layer was set up.

Referring to the classical surface contact theory, a "micro-peak and soft/hard plane" contact model was presented for analyzing the contact characteristics of soft film on hard substrate with its counterpart.

Based on the analysis of the physical change and geometry relationship of the contacting cylinder on two contacting bodies which subjected to a amount of perpendicular force in the friction process,the principal of the kinetic sliding friction is revealed,and the calculating formula for kinetic sliding frication factor is established.