Based on generalized Lorenz-Mie theory, the radiation forces exerted on defect particle on the wafer by a laser beam are derived combing the scattering theory about sphere particle to clean the defect particle in the optical nondestructive examination. According to relationship between spherical vector wave functions and triangle functions, the analytical expressions of the axial radiation force and the transverse radiation force exerted on defect particle by an Gaussian beam are given and the influences of many factors on the radiation forces are analyzed numerically in details. The results show that the maximum radiation forces become larger with the particle radius becoming less. The energy of optical axis and scattering forces become less with the particle radius becoming larger. The smaller the dielectric constant, the smaller the radiation force. In the project, the smaller beam waist widths is used with much more energy to clear the defect particle more efficiently. In addition, the defect particle material is detected by quantitative analysis to radiation forces.