The principle of interference imaging spectrometer is introduced. In this paper, ray tracing method is employed to present the rules of the prism Sagnac and the polariscope Savart in interference imaging spectrometer. The explicit formulae for the optical feux are deduced. The representative solutions such as the optical fluxes of Savart and Sagnac are both analyzed and compared. By performing the computer simulation, some important curves are obtained for the variations of optical flux with incident angle and wavelength. The work in this paper provides a theoretical guidance for the study of polarization interference imaging spectrometer.