Abstract: Nowadays, soil acidity severely restricts the production and development of orchard. But rational fertilization with different nitrogen forms can relieve soil acidification effectively. In this experiment, the authors used one- year- old apple rootstocks (Malus hupehensis Rehd.) as materials and 15N labeled tracer technique as the tool, designed 3 different nitrogen forms to test their effect on the growth and absorption, allocation and utilization of apple rootstocks under each soil pH gradient. The results showed that under different soil pH gradients, the plant biomass of three nitrogen forms treatment in acid soil from high to low was CO(NH2)2- N＞NH4 - N＞NO3-- N, which was significantly and positively correlated with soil pH; but the sequence in alkaline soil was CO(NH2)2-N＜NH4 -N＜NO3--N. Under different treatments of nitrogen forms and soil pH, the variation of Ndff value and 15N utilization rate in different organs of plant was significantly different. When soil pH 6.5, the value of total nitrogen content of plant treated with NH4 -N and NO3--N, reached the maximum of 0.47 g and 0.33 g. The 15N utilization rate of plant under different soil pH gradients was significantly influenced by nitrogen forms. Thus, the three nitrogen forms had significantly different effects on the plant index of nitrogen absorption, distribution and utilization under different soil pH gradients, which was the key factor limiting plant growth.