Standing wave total internal reflection imaging technique can obtain high resolution images of a sample along both axial and lateral directions. The variations of the interference patterns with incident condition of excitation light as well as refractive index of medium, and the differences between standing evanescent wave and standing propagating wave are theoretically investigated. The analysis shows that when contrast of the evanescent interference pattern is 1, optimal point spread function (PSF) can be obtained. Due to the narrowed FWHM of PSF, the lateral resolution increases with the decrease of period of the evanescent interference patterns. However, the intensity of PSF side bands increases, which will lower imaging quality.