The competition and ecological plasticity of fine roots between intercropping trees and alley crops are vital for the sustainable management in agroforestry system. To understand the interspecific competition and the adaptive strategy of fine roots in agroforestry system, both minirhizotron and soil core methods were used in investigating the dynamic of fine roots in the walnut-wheat (Juglans regia-Triticum aestivum) intercropping system at Weibei loess area. The monocultural systems were compared with the intercropping one. The results showed that there were two growth peaks of both walnut and wheat roots in the agroforestry system. One was from April to May and the other was from September to November. During April and May, large root biomass was gained and the major interspecific competition took place between walnuts and wheats. The root length density of walnut in the intercropping system was lower than walnut monoculture system at all the soil layers during all the growth periods. A significant difference was found since the 7^th year after planting. In surface soil (0-20 cm), the root length density of wheat increased rapidly from the 3^th to 7^th year in the intercropping system, and became significantly greater than the wheat monoculture since the 7^th year. However, the opposite trend was observed in the soil layer below 20 cm. The root ecological niche of walnut and wheat separated in the intercropping system. The roots vertical distribution center of walnut and wheat moved down for 6.59 cm and moved up for 8.59 cm than that in the walnut and wheat monoculture systems, respectively. In the aspect of root competition strategy, the wheat took competitive advantage through rapid growth and occupied more space in a short term than the walnut, however, the walnut trees took the space by accumulating their roots year by year and gradually took the advantageous place in the intercropping system. Walnut and wheat coexisted in the agroforestry system following the "competition-disturbance-rebalance" management strategy, which can interfere with the accumulation process of walnut root. In root morphology respect, wheat, whose fine root diameter was smaller at the beginning, tended to increase fine root diameter and reduce specific root length. However, the opposite trend was found for the walnut in the agroforestry system.