The method of measuring the intensity and state of polarization of optical radiation using polarization interference imaging spectrometer （PIIS） combines the basic theories of polarization interference imaging spectroscopy and polarization measurement technology. In this way, the PIIS can be used to detect not only the interference characteristics but also the polarization parameters. Based on the study of polarization measurement, this paper compares the effect of the degree of polarization errors for the conventional detection angles of 45°and 60°. The optimization of detection angle is then discussed, which will lead to a better angle choice for polarization measurements that enables the interference imaging spectrometers to be adapted to almost every field in which the spectroscopy has ventured and able to some where field which has not touched before.