<p>The spatial static polarization modulation interference spectroscopy, which enables the simultaneous acquisition of continuous spectral and polarization information without mechanical or electro-optical modulation components, integrates polarization spectral intensity modulation (PSIM) and spatial heterodyne spectroscopy (SHS). As one of the principal components of the system, the angular error from PSIM module is the primary source of the system’s measurement error and needs to be calibrated and compensated to enhance the accuracy. This paper aims to quantitatively analyze the impact of angular errors on measurement results by developing a mathematical model of the system. Angular errors were calibrated using the amplitude term of the reference beam and compensated via an enhanced demodulation algorithm. The numerical simulations and experiments were conducted to indicate that the measurement accuracy would be reduced due to the angular error of the PSIM module and the proposed calibration and compensation methods are valid. The experiment results demonstrate that when the fast-axis orientation error of the high-order retarder is 1°, the measurement accuracy can be improved from 0.0287 to 0.0136 by calibrating and compensating the error angle.</p>