Electronic components of weaponry are often used by combining with polymethyl methacrylate (PMMA) materials. PMMA will produce shock polarization and electromagnetic interference to electronic devices under high overload, which can be triggered by mistake. Therefore, it is of great significance to put forward the mechanoelectrical coupling model of PMMA under impact load. To reveal the mechanical-electrical coupling mechanism of PMMA and better characterize the polarization effect of PMMA under dynamic load, theoretical analysis, experiment and simulation are combined in this paper, the stress, capacitance and resistance of PMMA under different given loads were measured. The polarization characteristics of PMMA were tested by SHPB system and measurement system. Furthermore, the ABAQUS/Explicit-COMSOL co-simulation under corresponding experimental conditions is carried out. The results show that the resistance and relative dielectric constant of PMMA samples increase first and then decrease with the increase of strain. The flexural electric coefficients of PMMA at different strain rates are between 10−8 and 10−11. Meanwhile, an improved shock polarization model based on the Allison theory was proposed. Comparing with the experimental results, the error of polarization voltage obtained by this model is small, which can effectively characterize the dielectric and flexural electric effects of PMMA under dynamic load.