The multi-grid composite wall has unique structural types, and its stiffness can be adjusted according to different anti-seismic requests and complex architectural style. Referencing the frame-shear wall structure, the cooperative work mechanism and shear-sharing ratio calculation method of frame-composite wall structure are studied systematically in this paper. Based on the fundamental theory of Timoshenko beam, the frame-composite wall structure is regarded as double anti-seismic system consisting of shear type frames and shear-flexural type beams. The fundamental differential equation is established by the continuous approach, and its analytical solution of displacement and internal force are derived. Then the practical computational method of earthquake shear-sharing ratio on the frame-composite wall structure is put forward, and the influence degree that the composite wall rigidity degenerates to the structure internal force distribution is explained through concrete examples.