Abstract: Based on the characteristics of resistance spot welding of three-layer sheets and properties of zinc coating,1/4 model was established to numerically simulate the three-layer sheets. On the basis of experimental parameters,the nugget was investigated through optimizing the parameters. Then under the peak temperature,nugget formation and growth in different materials were analyzed with the optimized parameters. It was found that,comparing to the sheets without Zn coating,the Zn coating can affect the nugget formation,change the location of nugget nucleation and growing trend. For three-layer galvanized sheets, the nugget initially formed in the interface between two sheets without Zn coatings,and then grew radially and axially,finally penetrated three sheets. The simulated results agreed well with the experimental results.