A frequency response dynamic reanalysis method for a flexible plane truss includes that when that density of one element of structure is changed to produce mass perturbation, the total mass matrix iscalculated and the relationship between the total mass matrix and displacement frequency response matrix is determined. Based on the matrix correction formula, the modified structure response is calculated according to the initial displacement frequency response matrix, and the dynamic reanalysis of frequency response is completed. At first, that method of the invention obtains the displacement frequency response matrix of the flexible plane truss based on the finite element analysis, when the density of any element is changed, the change amount of the global total mass matrix is determined, based on the matrix correction formula and the initial displacement frequency response function, the corrected structural response is calculated and obtained, and the frequency response dynamic re-analysis solution is completed. Therefore, the dynamic analysis of the structure after mass perturbation can be completed by using the initial frequency response dynamic response signal and the local masschange of the structure without many finite element calculations, which simplifies the calculation efficiency, is more convenient and has practical engineering significance.