Abstract: In this paper, the interface cracks between the zinc coating and the 304 stainless substrate were investigated and the interface fracture toughness of the Zinc coating-elastic substrate system was obtained by three point bending tests installed with an acoustic emission device and microscope. The interface propagation length obtained by a finite element method (FEM) is in agreement with the experimental result. A finite element simulation by ABAQUS was conducted and the result shows that the interface fracture toughness is related to many factors. The interface crack propagation length increases with the increase of film thickness and external load, and it decreases with the increase of interface fracture toughness and elastic modulus, while Poisson's ratio has little effect on the crack propagation length.