The effect of the polarization and intensity profile of an incident laser on the resolution of a Laser Scanning Confocal Microscope (LSCM) was investigated.According to the vectorial diffraction integral of Wolf and Richards, a model of the illumination Point Spread Function (PSF) of LSCM with N-1 interfaces was established to calculate and analyze the PSFs on the zero interface and two interfaces.The analysis shows that for the zero interface, the local Full Width at Half Maximum (FWHM) of the PSF with circular polarization is 043 μm, which is rotationally symmetric in the xy plane, and the FWHMs along x axis and y axis of the PSF with linear polarization are 048, 039 μm,respectively in the x axis.As the filling parameters of a Gaussian light are 0, 1, 2, 5, the FWHMs of the PSF with circular polarization are 043, 047, 062 μm and 149 μm,respectively. For two interfaces, when the probe depth is 50 μm, the FWHM of the PSF with circular polarization is 026 μm, and the FWHMs along x axis and y axis of the PSF with linear polarization are 028,024 μm,respectively in x axis; for the filling parameters of 0,1,2,5, and the probe depth of 50 μm, the FWHMs of the PSF with circular polarization are 026, 028, 032 and 068 μm,respectively. Calculations metioned above show that the resolution of the circularly polarized light is better than that of the linearly polarized light in one direction, but it is worse than that of the linearly polarized light in the perpendicular direction. The PSF with the circularly polarized light is rotationally symmetric in the xy plane, therefore, a better image can be obtained. The smaller the filling parameter is, the better the resolution of LSCM is.