In this paper, the friction law characterized by the function of contact slide length and strain of a zinc-coated steel sheet is established through experimental observation. SEM observations of tension and bending tests, hardness and roughness tests and friction test of electrogalvanized (EG), galvannealed (GA) and galvanized (GI) steel sheets have been done. The formability of three types of coated sheet of square-cup deep drawing is investigated by elastic-plastic finite-element simulation. These show that l) frictional characteristics can be evaluated from the function of slide length and strain ; 2) the difference of frictional characteristics of the coated sheets induces the difference in strain localization and formability.