Abstract: The stress-strain field of interface crack tip inorthotropic bi-materials is determined by photoelastic coating in thispaper, and the fracture mechanics parameters for interface crack arederived. Orthotropic bi-materials panel is made into a tension specimen,and metallic-aluminum coating is plated in the surface of unilateralpolycarbonate coating to enhance the reflectivity of polycarbonate coating.Then the load along the interface prefabricated cracks of bi-materials isgradually increased, a series of clear equi-difference lines canbe observed. Stress intensity factor can be calculated by using stresscomponent expressions for interface crack in orthotropic bi-materials. Thetesting-result indicates that photoelastic coating can effectively analyzethe problem for interface crack in orthotropic bi-materials.