Abstract: To study the relationship between growth traits and biomass of Pinus yunnanensis Franch. seedlings, 2-year seedling in the greenhouse of Southwest Forestry University were cultivated whose seeds were collected from Lufeng, Yiliang and Kunming, Yunnan Province. The growth traits (seedling height, ground line diameter, major root length, lateral root length, needle length and number of lateral root) and biomass were measured and analyzed. Correlation and path analysis were used in the relationship between them. The growth traits and biomass of P.yunnanensis seedlings were significantly positively correlated with each other. By path analysis, there was the positive direct path coefficient to the biomass of each component for the each growth traits. The most effect on the biomass of each component were the ground line diameter and seedling height. Needle length, lateral root length and major root length had the positive direct path coefficient to the biomass of each component. The direct path coefficient to the biomass of each component were obviously bigger than indirect path coefficient. The lateral root length has the biggest indirect effect on the biomass of each component through other traits. According to the correlation and path analysis, the biomass model were set up by using growth traits, which can be used in estimating the biomass for P.yunnanensis seedlings.