This paper present a energy-based modelling approches for interfacial debonding between steel and concrete. 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 is modeled as crack propagation along the interface. The energy relationship is discussed in the process of debonding and an energy-based criterion for steel-concrete composite structure is proposed. Following, the debonding process is analyzed through energy-based criterion. The analysis is first performed for special case with constant shear stress along debonded interface, and then for the general case with shear stress softening in the debonded zone. A direct correspondence between energy-based and strength-based analysis can be established for arbitrary softening behavior along the interface. Specifically, through the proper definition of effective interfacial shear strength, the conventional strength-based approach can be employed to give the same results as the much more complicated energy-based analysis.