The accuracy of polarized detection for field-portable spectropolarimeter directly influences the precision of polarization spectrum of ground object, and thus affects the interpretation accuracy of the polarized characteristic of targets. A polarization measurement group unit was designed for grating spectrometer. Then the two kinds of grating spectrometers were transformed into spectropolarimeters. Based on variable polarization light source, the performances of the two spectropolarimeters were verified. The polarization sensitivity of the two spectropolarimeters was analyzed at first. The different degree of polarization spectra output from variable polarization light source was measured using the two spectropolarimeters. The results show that both of them have polarization sensitivity and the degree of polarization of output light measured by the two spectropolarimeters are consistent with the theoretical output of the variable polarization light source. The error between theoretical output and measured results are within 2% when the wavelength range is from 460 nm to 920 nm. It verifies that the feasibility of two spectropolarimeter polarization measurement group unit which could meet the experiment requirements.