It is generally found that enhancement in catalytic activity comes at the expense of selectivity or stability. In this study, a sulfur-modified Mn₂O₃ (S-Mn₂O₃) solid catalyst was prepared using a simple oxalate precipitation method. This catalyst exhibited not only high catalytic activity but also high selectivity and good cycling stability. The degradation ratio of bisphenol A (BPA) under S-Mn₂O₃ activated peroxymonosulfate (PMS) achieved over 99% within 10 minutes, and the mineralization ratio increased to 83.2%. Particularly, the degradation rate for BPA under of S-Mn₂O₃/PMS system was 15 times that of Mn₂O₃. Furthermore, the degradation ratio remained at 93.3% after five consecutive cycles. Multiple experimental characterizations confirmed that the introduction of S into Mn₂O₃ shifted the oxidative degradation pathway from a mixture of radical and non-radical routes to a predominantly non-radical pathway. This suppressed radical generation promoted the selective formation of high-valence metallic oxygen (HVMO) species and singlet oxygen (¹O₂), thereby significantly enhancing the catalytic activity. In addition, the S-Mn₂O₃/PMS system exhibited broad applicability towards the degradation of other phenolic pollutants, strong anti-interference capability against complex water matrices, and suitability for efficient removal of organic contaminants in such environments. This research offers new perspectives for the design of selective catalysts for PMS activation.