In order to settle the influence of measuring results of particles with its shape-variety, the shape-influence factor of arbitrary particles in Gauss scattering field is discussed based on the half-ellipse model, the mathematic relation between the shape-influence factor and size and shape of particles is rebuilt, and the distribution of numerical-solution of the influence factor is obtained. The analytical formula solution of the influence factor is fitted in Gauss scattering field based on the studying of the dynamical characteristics of it. Then the perturbation equation about the probability distribution characterized-function of arbitrary particles is improved. It shows that this method is very useful for partides with large diameter in the shape-modifying.