Against the backdrop of “dual carbon”, urban forests, as an integral carbon pool within the city, play a critical role in mitigating climate change. Quantifying the carbon-fi xation capacity of regional-scale forests is of great signifi cance for evaluating the ecological functions of urban forest green spaces. Based on remote sensing and fi eld monitoring data from April 2025, relevant characteristic factors were extracted, and a multiple stepwise regression model was constructed to estimate the study area’s carbon density and analyze its spatial distribution. The results show that: (1) The cumulative frequency of vegetation carbon density conforms to a normal distribution, with a linear regression model R2 of 0.858 and an RMSE value of 22.846, indicating reliable prediction results. (2) The carbon storage of Nanjing Hongshan Forest Zoo is 9 031.90 t, with an average carbon density of 150.5 t/hm2. The overall spatial distribution of carbon density shows a pattern of higher values at the edges and lower values in the middle. (3) The proportion of high carbon density distribution on the shady slopes is higher than that on the sunny slopes. In the vegetation carbon density ranges of 0 ～ 50 t/hm2 and 200 ～ 250 t/hm2, there is a trend of decreasing distribution with increasing slope; when vegetation carbon density is 200～250 t/hm2, it shows an increasing distribution trend with rising altitude. The research results can provide a reference for assessing the carbon sink capacity and ecological functions of urban small-scale forests.