A kind of simultaneous imaging polarimeter with a high spatial resolution for satellite platform environments was designed which was based on an off-axis three-mirror system as front-view telescope system and combined with simultaneous-amplitude polarization imaging technology, and the simultaneous polarization imager was designed to simultaneously acquire the target Stokes parameters to suppress sea surface glare, sea fog, atmospheric radiation and other disturbances. It provided an effective means to improve the contrast of detection targets, and had obvious advantages in dynamic target detection. According to the optical system, the detailed structural design had been finished. Finally, through the laboratory performance test, the working spectrum was 500-700 nm, the FOV was 8.5°×0.1°, the spatial resolution was 5 m@500 km, the optical MTF was more than 0.4@71.4 lp/mm, and under the condition of an elevation angle of 30° and a reflectivity of 0.2, the noise ratio was better than 38 dB, the polarization measurement accuracy is better than 1%(P≤0.3), the first-order mode of the whole machine was 195 Hz, and it had good strength and stiffness. The overall performance meets the actual use requirements.