Abstract: Composite sandwich structures are widely used in many fields due to their high strength to weight ratios, high stiffness to weight ratios, anti-corrosion ability and other characteristics. However, the structures are faced with a variety of injuries under active conditions. Actually, in the existing applications, the open type delamination (mode I interfacial delamination) between the surface layer and the core material is a common failure mode under the coupling effects of temperature and loads. Based on conservation of energy and elastic foundation beam theory, expression of strain energy release rate is analyzed, while the crack between the surface layer and the core material is expending. At the same time, according to the contrastive analysis between the calculated values and experimental values of sandwich double cantilever beam (DCB), the correctness of the expression of strain energy release rate under the coupling effects of temperature and loads can be verified.