A multiparameter model-guided polarization optimization method is proposed for polarization effect correction of a dual-coded snapshot spectropolarimeter. A full-link polarization effect model of the spectropolarimeter based on a digital micro-mirror device （DMD）， prism-grating-prism （PGP）， micro-polarizer array （MPA） detector， and multi-film system is established. Bidirectional attenuation of the spectropolarimeter with incident partially polarized light is analyzed. The relationship among wavelength， polarization degree of the incident light， and polarization effect is revealed. The polarization effect of the spectropolarimeter is optimized through targeted control of the refractive index and incidence angle， grating refractive index and constant， prism refractive index and top angle， and film refractive index and film thickness when the spectral line bending meets the reconstruction requirements. The simulation results show that the structural similarity （SSIM） of the optimized system is >0.8 and that the relative error of the system polarization effect is <4%. The polarization effect is reduced by at least 6% compared with that before optimization. When the polarization of the incident light is constant， the polarization effect of the system is inversely proportional to the wavelength. The experimental acquisition of spectral polarization reconstructed images of typical materials under a single exposure improves the relative error by at least 14.7% for metal and 63.6% for plastic. The necessity and feasibility of the proposed polarization optimization method are verified. This study lays a theoretical foundation for high-precision acquisition of multidimensional data in dual-coded spectropolarimeters.