Abstract: 【Objective】 To explore the distribution characteristics of black walnut root in soil, and provide a theoretical basis for the efficient management of the water and fertilizer.【Method】5a black walnut was used as a test material, the biomass density, root surface area density and total root length of root system in different soil layers were analyzed by means of soil excavation and stratified sampling and the plant image analysis system and the drying weighing method.【Result】The root biomass density, root surface area density and total root length density showed a decreasing trend in the vertical and horizontal direction. In the vertical distribution, the deepest vertical distribution of the root system reached the soil layer of 150 cm. 0-70 cm layer area was the main one of the vertical distribution of root, the root system biomass accounted for 85.45% of the total vertical distribution. The maximum value of root surface area density and total root length density were distributed in the soil layer of 0-10 cm, which were 17.66 mm²/cm³ and 0.34 cm/cm³, respectively. In the horizontal direction, the farthest distribution of the horizontal distribution was above 120 cm, the distance between the tree trunk and 0-80 cm was the main area of the distribution of root biomass. The root biomass accounted for 93.98% of the total level of distribution. The maximum root surface area density and root length density were distributed in the soil layer 0-20 cm from the tree trunk, which were 0.12 cm/cm³ and 0.43 cm/cm³, respectively.【Conclusion】5 years old black walnut root system vertical deepest distribution reached 150 cm soil layer, horizontal distribution of the farthest distribution reached 120 cm. The root distribution of black walnut was mainly located in the area of 0-80 cm from the trunk, and the area of 70 cm deep is the main area of root distribution of black walnut, and the soil layer should be the key area of fertilizer and water management 70 cm deep. This soil layer should be regarded as the key area for the management of fertilizer and water.