Abstract: A steel-concrete composite structural member is considered as a generalized elastic body with both the applied load and the interfacial shear stress acting as boundary stresses, and the debonding process is modeled as crack propagation along the interface. The energy principle in fracture mechanics is used to derive the energy relationship in the process of debonding, and an energy-based criterion for steel-concrete composite structures is proposed. The analysis is first performed for a special case with constant shear stress along the debonded interface, and then for a general case with shear stress softening. The theoretical solution for the interfacial bond strength is obtained. The same expression for the bond strength is attained whether the softening is considered. The solution for the bond strength is influenced by material parameters of interlayer concrete, including fracture energy, depth, as well as shear modulus.