[Objective] The impact of reed-based exogenous carbon on soil properties and organic carbon stability was investigated to provide theoretical insights into the application of reed resource materials for soil improvement. [Methods] A 60-day soil culture test was conducted for the application of various exogenous carbon materials, including reed aerobic compost (compost T₁ conditioned with biochar and compost T₂ conditioned with sediment and biochar), straw (RS), and biochar (RB). The effects of different exogenous carbon sources and amounts (5%, 10%, and 15%) were analyzed on the physicochemical properties, enzyme activities, and organic carbon mineralization of the soil. [Results] The application of exogenous carbon influenced the soil nutrient content, with the soil organic carbon content in the experimental group increasing significantly by 28.0%—64.2% compared to that in the control group (p<0.05) at the beginning of the culture. Compared with the initial stage, the organic carbon content of the soil supplemented with biochar and compost at final stage was significantly reduced by 15.5%—23.5%, whereas the total nitrogen content of the soil at final stage decreased by 20.0%—69.1%. The concentrations of β-glucosidase and dehydrogenase increased following the addition of exogenous carbon, with the most significant effect observed for biochar and compost. The β-glucosidase and dehydrogenase contents in the soil presented highly significant positive correlations with the soil bulk density, carbon source content, and total nitrogen (p＜0.01). The cumulative mineralization of organic carbon in the soil following the addition of exogenous carbon during the culture experiment exhibited first-order kinetics, while the soil organic carbon mineralization in the straw and biochar treatment groups was 652.9—758.2 mg/kg, which was significantly higher than that in the control group (532.8 mg/kg) and T2 composting (598.3—623.7 mg/kg) treatments. The amount of exogenous carbon added significantly influenced the soil organic carbon mineralization. [Conclusion] The addition of reed-based exogenous carbon improved soil physical and chemical properties and significantly enhanced enzyme activities. The excitation effect of reed straw on soil organic carbon mineralization was significantly greater than that of biochar and compost.