In order to study the spatial distribution feature of walnut tree root, this article used the layered sublevel mining method to study the total root length walnut tree, root weight, effective absorption root and the rule of spatial distribution under the mode of drip irrigation in arid areas. The research has shown that trees roots at horizontal direction are mainly distributed in 0-120cm, accounted for 90.84% of the total distribution; Vertical direction are mainly distributed in 0-90cm, accounted for 78.75% of the total distribution. Root weight at horizontal direction are mainly distributed in 0to 30cm, accounted for 52.49% of the total distribution; tree roots at vertical direction are mainly distributed in 15-75cm, accounted for 61.12% of the total distribution. Effective root length of suction is the distribution areas of concentration of 60cm at horizontal direction and 60cm at vertical direction . The root zone at 60cm horizontal distance and vertical depth of 60cm from trunk should be taken as the key area of water and fertilizer management of walnut tree.