The invention relates to a method for establishing a linear link energy function and application, and belongs to the technical field of theory of electrical engineering and generator control. The method includes realizing equivalence of a linear link represented by a transfer function with an RC circuit, and using an energy function built by the equivalent circuit as an energy function of the linear link. The method provided by the invention applies the equivalent circuit to indirectly obtain the energy function of an element, solves the problem of linear element energy establishment, and provides assistance for solving the problem of modeling of a complex system on the whole; and the method can be expanded and applied to wherever energy establishment of a linear element is needed.