The internal force calculation of statically indeterminate structures is the key and most difficult point in the course of structural mechanics. When degree of statical indeterminacy is large, it is very difficult to calculate with traditional methods and it is not easy to understand. The idea of force equivalent structure is summarized in this paper. The force-equivalent structure is completely equivalent to the original structure in terms of internal forces and deformations. Based on this idea, a new method for internal force calculation of complex statically indeterminate structures is proposed, which is thereafter applied to both the displacement method and the hybrid method to solve multiple statically indeterminate complex structures. Compared with traditional methods, the feasibility of the proposed force equivalent structure idea is verified. The proposed method can greatly reduce the number of basic unknowns of complex statically indeterminate structures, simplify the calculation process and improve the solution efficiency.