Abstract: The basic principle and current state of slip-line field theory for sliding metallic contact friction were introduced in this paper. The deformation of soft metal asperity caused by hard edge sliding, which was used as the basic model of sliding metallic contact friction. The involved strain and stress were analyzed and equations were derived for coefficient of friction. The study revealed that the interaction between adhesion and ploughing items, which were separated in the adhesion theory. Experimental results are in good agreement with the theoretically predicted results. The relationship between Archard' s wear coefficient and the critical number of deformation cycles to fatigue failure was estabished quantitatively. The significance and future trends of the study are also reviewed.