Abstract: Experiments were designed to test the absorption, allocation, and utilization of urea-15N by 2 years-old M. hupehensis Rehd （YanFu/M26）under different N rates in the current year and next year. The results show that both the rational application rate of nitrogen fertilizer (N100) and overuse rate (N200) could promote the growth of trees and their15N utilization rate in the current and following year significantly. Nitrogen application could promote the development of roots, benefiting the growth of shoots as a results.. The N100 treatment has better promotion effect than the N200 treatment on the shoot growth. The most obvious promotion of N fertilizer to the root growth happens during the period from fertilization to the vigorous growth of autumn shoots and the end of spring shoots growth stage, the obtained ratio of root to shoot is in order of N100＞N200＞N0，and the allocation of15N in roots is in the same order with the value 42.93%, 37.10% and 26.39% at the vigorous growth stage of spring shoot, and 28.61%, 20.30% and 14.27% at the end stage of spring shoot growth stage, respectively. The growth vigor of N100 treatment is superior to the N0 treatment till the stage of vigorous growth of autumn shoots, with no significant difference is found on15N distribution ratios of both. The aboveground15N distribution ratio of the N100 treatment (85.93%) is significantly higher than N200 treatment (77.28%), while the root ratio (14.07%) is significantly lower than N200 treatment (22.72%). Compared with the N0 and N200 treatments, the biomass weight of the N100 treatment is increased by 75.83% and 76.41% respectively till the vigorous growth stage of spring shoots the next year, while the root to shoot ratio and root15N distribution ratio of N100 are significantly lower than the N0 and N200 treatments. Even with a high root to shoot ratio and root 15N distribution ratio, N200 treatment is not suitable for growth. The defoliation in winter is the main nitrogen loss of dwarfed interstock apple saplings, accounting for 44.56%-51.25% of total nitrogen uptake in current year.