Abstract: When a surface is illuminated by laser, the field of diffusing reflectivelight can be described by Fresnel-Kirchhoff integration in the region of Fersnel. If the correlation, before and after the change of intensity field, is analysed by statistical method, three governing equations for variance of intensity field and speckle movement formula can be obtained. In these equations.the surface motion, deformation and wavelength change are all considered to cause the speckle movement.