Polarimetric detection, a critical technical approach for characterizing light–matter interactions, has been widely applied in biomedical imaging, high-precision optical metrology, and military target identification in recent years. To address and fulfill the development requirements for integration and miniaturization of optoelectronic systems, an innovative full-Stokes polarimetric detector, based on the silicon-on-insulator (SOI) technology, is proposed in this study. In this design, a 500 nm-thick SOI device layer is selectively patterned to form a metasurface structure and simultaneously engineered as a pin photodetector. This approach enables monolithic integration that effectively addresses the critical limitations of conventional polarization detection systems, i.e., their bulky form factors and poor integration capability. The results demonstrate excellent device performance at the operational wavelength of 780 nm, where the chiral metasurface pixels exhibit circular dichroism of 42%, and the linear metasurface pixels achieve an extinction ratio of 10 dB. Notably, high-accuracy Stokes parameter reconstruction is accomplished, with average measurement errors of 0.30%, 0.85%, and 11.17% for the parameters S₁, S₂, and S₃, respectively. This study provides a novel design strategy for integrated polarimetric systems as well as highlights the considerable application potential of metasurface technology in the field of optoelectronic integration.