Abstract: By collecting 650 trunk biomass samples of Pinus armandii with different diameter levels, the biomass ratios of trunk, wood, and bark within and among different diameter levels were compared and analyzed. The results showed that the percentage of biomass of trunk, wood and bark in the upper part was the smallest, the middle part was the second, and the lower part was the largest; among different diameter order groups, with the increase of diameter order group, the proportion of upper biomass of trunk, wood and bark gradually increased, the proportion of middle biomass did not change much, and the proportion of lower biomass gradually decreased.