The polarization-difference interference imaging spectrum system with adjustable optical path based on the combination of the angular shear of Wollaston prism and the lateral shear of Savart polariscope, can not only simultaneously obtain the two-dimensional space image and the interference image in the orthogonal polarization direction of the target, but also obtain the interference image in the orthogonal polarization direction under different optical path differences by adjusting the thickness of Savart polariscope. The features of the system are simultaneous acquisition of orthogonal images and real-time adjustment of optical path. The structure and theoretical principle of the polarization-difference interference imaging spectrum system with adjustable optical path are demonstrated. Expressions for the interference intensity are derived as well. The variation ranges of the optical path difference and the lateral displacement for the modulated Savart polariscope (MSP) and the modulated wide-field-of-view Savart polariscope (MWSP) are analyzed in detail. Through the contrast it is concluded that the optical path difference is little while the lateral displacement of MWSP is 50% higher than that of MSP. The results provide important evidence for the type selection of the Savart polariscope.