Biomass data of 32 Chinese fir sample trees (7-26 years old, 5~25 centimetre diameter breast height) have been investigated. The relationship between DBH(x) and stem weight(y) can be expressed by the regression equation y = a(x2H)b. The exponential equation y = aebx appears to be the closest correlation between DBH and root weight, branch weight and needle weight.The biomass of the Chinese fir stands at the age of 7, 9, 11, 16, 19, and 26 years on Yangkou Forestry Farm are 61.6, 78.4, 85.6, 110.8, 125.5 and 139.7 tons per hectare respectively. With the increase of tree ages, the proportion of stem weight increases, while those of root weight, needle weight and branch weight decrease. Special structures of Chinese fir stand biomass at different ages are compared. Analyses of the average annual net production of the Chinese fir stands and the relation between the age and the assimilation rate of needles are made, which show that the quantitative maturity of Chinese fir stands occurs when they are 19-20 years old.