Abstract: In this paper, the seedling biomass of Sapindus mukorossi of accumulation and distribution laws was analyzed quantitatively, the growth allometric equation of seedling root and stem biomass was formulated, and the correlation of each organ, whole plant between seedling height, ground diameter was described by means of SPSS regression analyzing. The results showed that: the annual biomass accumulation of the oneyearold Sapindus mukorossi seedling could be divided into three stages, including the seedling stage, fastgrowing period, later stage. The allocation proportion of root biomass was the least in seedling stage, but leaf was the largest, respectively accounting for 1685 % and 5880 % of the whole plant. Entering the fastgrowing period, the center accumulation of biomass gradually transferred to the roots and stems, the stem become the most center of biomass accumulation, accounting for 6155 % of the total plant biomass. At the later stage of growth, root and stem were further lignified, the biomass allocation proportion of leaf reduced sharply because leaves falling, only accounting for 1144 %. The different speed of biomass accumulation of root and stem, and seedling biomass of each organs, whole plant, and ground diameter, height growth both showed extremely significant correlation, the mathematical model was high reliability, could be used to guide the practical production.