Through a dynamic study on one-year seedlings from seeds of Azadirachta indica, the annual growth model, conti～auous day growth model and daily average growth model were created. According to these fitted models, the growing dynamics of seedlings could be divided into 4 stages, i.e. emergence phase(from the middle ten-day to" the last ten-day of October), initiation phase(from the first ten-day of November to the middle ten-day of April next year), prosperous phase(from the last ten-day of April to the last ten-day of September), later phase of seedling(from the first ten-day to the last ten-day of October). The functional model about height and ground diameter with the biomass of seedling indicated that the biomass of seedling(including aboveground biomass, underground biomass and the total biomass) was closely related to the growth of height and ground diameter of seeding. The total dry weight was 38.8% of the total green weight, and tbe aboveground dry weight was 26.8% of the total green weight and 69.1% of the total dry weight. Meantime, according to convention, and the reference index of height and caliper, the quantitative grade standard of nine-month seedlings of A. indica was divided. The experiment of forestation was carried out according to the seedling’ s quantitative grade standard. The results showed that the quantitative grade standard of A. indica seedlings in 3 grades was reasonable and feasible. But only Grade I and Grade lI seedlings could be used to afforest.