Abstract: Based on the forest resource map data of Mojiang county in 2020, the biomass expansion factor method was used to estimate the biomass, carbon storage and carbon density of Pinus kesiya var. langbianensis in Mojiang county, and the effects of four factors including different age groups, different diameters and different geomorphic factors(slope position and aspect) on the biomass, carbon storage and carbon density of Pinus kesiya var. langbianensis were analyzed. The results showed that the biomass and carbon storage were proportional to the stock, and increased with the increase of stock. The carbon storage ratio of young forest, middle forest and near mature forest in Pinus kesiya var. langbianensis of Mojiang county was more than 97%. The area of mature forest and over-mature forest was relatively small in Mojiang county, but the carbon storage density was large. There was no significant difference of carbon storage density in different slopes of Pinus kesiya var. langbianensis plantation in Mojiang county. The carbon storage density of Pinus kesiya var. langbianensis plantation and natural forest showed as follows in different slope directions:north > northeast > northwest > west > east > southwest > south > southeast.