Abstract: An interfacial potential barrier theory to calculate friction and wear is proposed by considering micro interaction of frictional surfaces. In the theory, it is suggested that the performance of friction and wear depend on the magnitude and distribution of interfacial potential barrier on the contact surfaces. Then, the calculation methods of interfacial potential barrier and standard interfacial potential barrier were studied and the formulas to calculate friction force, friction coefficient and quantity of adhesion wear were derived according to the theory. The standard interfacial potential barrier can be used as an index to describe the frictional performance of material due to its independency and stability. The calculation results of friction force with some known experimental data are consistent with the experimental results carried out with an ultra high vacuum atomic-force microscope, and it shows that the theory is feasible.