In order to improve the accuracy of the eigen problems solution of rotationally symmetrical structures with interpolation methods offered in [1], the present article develops a kind of methods in data-processing that can reduce the errors of some numerical methods. In this paper, the author mainly deals with the application of the methods in Lagrange interpolation, paying particular attention to its comparison with the commonly used Interpolation methods. These new methods have proved to be efficient and reliable, as verified by the results of experiment and computation.