The resolution of lithography has become higher and higher to satisfy the demand of the continuous reduction of integrated circuit critical dimension(CD). As to the Rayleigh criterion, the resolution of optical projection lithography can be enhanced by reducing the wavelength, lowering the process factor and enlarging the numerical aperture(NA). As NA becomes larger, the polarization of light affects the imaging more significantly. By using the polarized illumination, the resolution can be improved. The reason why the polarization of light affects the imaging is analyzed by interference principle. The imaging of different polarized light is simulated with the Abbe’s theory of image formation and vector’s property. The image contrast and Depth of Focus(DOF) under different polarization are compared. The result shows that imaging performance can be improved by optimizing the polarization of illumination.