Abstract: Taking the natural forest of Pinus yunnanensis in Dali of Yunnan Province as the research object, the sample data of the fourth to seventh continuous forest resource inventory in the study area, the biomass estimation model of P. yunnanensis natural forest by remote sensing was developed. Based on the data of the 2006 forest management inventory in Yunnan Province, biomass inversion of P. yunnanensis natural forest in Dali was carried out. The biomass change of P. yunnanensis natural forest was analyzed from 2 aspects of spatial distribution and temporal change. The results show that biomass is most abundant between 1500−3000 m above sea level, accounting for 94% of total biomass; the slope analysis shows that the P. yunnanensis natural forest biomass increases first and then decreases with the gradual increase of slope, mainly distributed at 5°−35°, accounting for about 94% of the P. yunnanensis natural forest vegetation biomass; in terms of slope aspect, the biomass of P. yunnanensis natural forest was evenly distributed in the study area, mainly distributed on the semi-sunny slope(west slope, southeast slope) and sunny slope(south slope, southwest slope), accounting for about 48%−54% of the P. yunnanensis natural forest biomass. In general, the P. yunnanensis natural forest area, average biomass and biomass of P. yunnanensis natural forest in Dali increased during the past 15 years, and the P. yunnanensis natural forest cover area increased and the overall forest biomass increased.