Abstract: Manganese-based metal halide perovskites have attracted significant attention due to their excellent photoelectric conversion efficiency and low-cost preparation advantages. Among them, cesium manganese chloride (CsMnCl₃) has emerged as a promising candidate for spintronics and magnetic applications. Understanding the structure-property relationship of CsMnCl₃, particularly its behavior under extreme conditions, is crucial for developing stable and efficient manganese-based perovskite materials and expanding their application scenarios. In this study, we systematically investigated the structural and optical properties of CsMnCl₃ using diamond anvil cell (DAC) technology combined with in-situ high-pressure photoluminescence (PL) spectroscopy, absorption spectroscopy, Raman spectroscopy, X-ray diffraction (XRD), and first-principles calculations. At ambient pressure, CsMnCl₃ crystallized in the R3 ̅m space group. During compression, we observed a structural transition at approximately 0.9 GPa, accompanied by a significant enhancement about 8.4 times in the photoluminescence intensity of CsMnCl₃. Within the experimental pressure range from 0 to 32.2 GPa, the optical bandgap gradually decreases by about 28% with increasing pressure. Our findings provide theoretical support and experimental evidence for optimizing the high-pressure stability of manganese-based perovskite materials and expanding their functional applications under extreme conditions. Additionally, the fundamental understanding of metal halide perovskites under high pressure is enriched.