In this paper, red soil samples from Yingtan, Jiangxi and Jindun, Yunnan and alluvial soil samples from Fengqiu, Henan were collected to investigate the degradation of triclosan (TCS) in agricultural soils in the presence or absence of manganese oxides. The effects of manganese oxide concentration and organic acid types and concentration on TCS degradation were also investigated. The degradation products of TCS were analyzed by HPLC-TOF-MS to explore the oxidative degradation of TCS by reactive manganese oxides in soil. The results showed that MnO₂ could oxidize TCS in varying degrees in three different soil types at a water-soil ratio of 4:1, and the strongest oxidation capacity of TCS was observed in acidic soil (red soil from Yingtan, Jiangxi), followed by red soil from Jindun, Yunnan. It indicated that the oxidation capacity of MnO₂ was negatively correlated with soil pH. In addition, the degradation rate of TCS increased with the increasing concentration of manganese oxides in soil, and the degradation rate of TCS reached 81% within 8 h at 50 g/L MnO₂. There was a linear correlation between the kinetic constants of the first-order reaction and the concentrations of manganese oxides. The presence of small organic acids, such as oxalic and citric acids, significantly inhibited the degradation of TCS, but tartaric acid promoted it. In addition, the oxidative polymerizations pathway of TCS were proposed based on the detected dimers products. This study provided a new vision for understanding the attenuation and remediation of TCS in contaminated soil.