Composite materials with its superior performance are more widely used in the field of shipbuilding. As a typical engineering structure, steel-composite with heterogeneous property has the dynamic characteristics different from that of a single homogeneous system. As the actual structure is generally more complex, it is difficult to directly determine the composition of the subsystems involved in vibration or noise radiation in the composite structure. In order to obtained the subsystem that are involved in the vibration of the composite structure, based on the analysis of the master-slave vibration mode and damping dissipation mechanism of heterogeneous composite system, combining with statistical energy analysis principle on the loss factor classification description, the damping law of the composite system was analyzed. The loss factors and the energy proportion of the dominant vibration subsystem of steel-composite system were calculated and compared. The results show that after eliminating the effects of radiation loss and boundary loss, the internal loss factor of the heterogeneous composite system close to the material loss factor of its dominant vibration subsystem in magnitude, and between each subsystem of material loss factor value. The modal recognition of a typical combination system is completed, and the feasibility of using the loss factor composition rule to identify the dominant vibration subsystem is verified. The deficiency of complex non-homogeneous composite structure in modal recognition is made up.