The invention provides a Legendre modeling method for an aircraft flutter analysis grid model and aims to solve the problem that the prior art cannot effectively express a complex flutter model underthe influence of aerodynamic force and intensity variation. The method has the advantages that multiple grid points on an aircraft body shaft system are selected, the complex flutter grid model is represented according to a body shaft system decomposition method under the influence of aerodynamic force and intensity variation such as different flight speed, atmospheric density, airflow environments and different temperature, sensor and data installation and image recording requirements are put formed according to requirements for building the model, data is acquired through effective flutter flight tests, a excitation function is acquired according to the measured value of an airflow sensor, a Legendre function is used to perform approximation and equivalent description on vibration variables, the solution of three axial vibration equations at the grid points of the body shaft system is determined at the same time according to an identification method, and the technical problem that the prior art cannot effectively express the complex flutter model under the influence of aerodynamic force and intensity variation is solved.