The infrared polarization properties of target can be measured by polarimetric Fourier transform infrared (FTIR) spectrometer. In order to obtain spectral radiance distribution of target, the instrument must be calibrated in infrared waveband. The experimental results indicate that the instrument response functions of the polarimetric FTIR spectrometer are inconsistent at different polarized orientations. It was caused by the instrumental polarization sensitivity. The polarization characteristics of the instrument were measured and instrument response function and its offset were acquired. The influence of instrumental polarization sensitivity is eliminated using the result of calibration, which can be employed as the foundation for improving the polarized accuracy of the infrared target detection.