In order to analyze the effect of Schmidt prism′s polarization aberration on the imaging quality with the widely used un-polarized light, based on diffraction intensity distribution of polarized light vector and by using two incoherent superposition integral methods, the same diffraction patterns as un-polarized light passing through the Schmidt prism are obtained. According to the equation of diffraction pattern, the polarization aberration consists of doubling of the image after the un-polarized passing through Schmidt prism and they are symmetrical. Analysis results of the central intensity ratio, resolution and the surface deformation defined in this paper show that the imaging quality of Schmidt prism is severely affected by the polarization aberration. B, one of the Jones matrix factors, as the structure characteristic of prism parameters, influences and determines the quality of imaging prism. The value of B indicates the size of polarization aberration of Schmidt prism. Both theoretical analysis and experimental results show that, the best condition for correction of Schmidt prism polarization aberration is B=0.