It is of great significance to investigate the effects of intercropping leguminous crops on soil moisture, nitrate nitrogen content and tree growth in young orchards for the improvement of soil fertility and sustainable development of dryland orchards on the Loess Plateau. Taking apple-soybean compound system in the loess hilly-gully region as the research object, the influence of different density of intercropping soybean on fruit tree growth were evaluated by measuring the changes in water and nitrate nitrogen content, as well as the nitrogen content and physiological indicators of fruit tree leaves in the experimental plot during the entire reproductive period of soybean planting. The results showed as follows:(1) Compared with clear tillage orchard, medium density intercropping had a certain effect on the soil moisture content of orchard before soybean flowering, while high density intercropping increased the water consumption between rows and significantly reduced the soil moisture content. (2) The relative accumulation of nitrate nitrogen in different soil layers gradually decreased and the distribution gradually balanced with the reproductive period of soybean, and there was no significant difference in the total nitrate nitrogen accumulation of soil between treatments. (3) Both medium and high density intercropping could effectively increase the leaf nitrogen content of fruit trees and promote fruit trees growth. Soil water content and leaf nitrogen content of medium density soybean intercropping increased by a maximum of 17.6% and 8.04% respectively. Therefore, medium density soybean intercropping had more advantages in dryland apple orchards on the Loess Plateau.