It is the primary factor to influence the completion and utilization efficiency of water and fertilizer for the root distribution in strip intercropping field. The effects of 3 treatments of high, middle and low irrigation quotas on soil water of different positions and root distribution were studied, and the characteristics of root distribution in different growth period were investigated, as well as the pattern of root distribution in vertical and horizontal direction based on cumulative root distribution curves. The results show that the average soil water in tomato side is obviously higher than corn side, and the soil water under mulch is also obviously higher than that under outside mulch; however, there is no significant difference for the soil water of different positions under mulch. With crop growth, there are the pattern of “no cross—small cross—full cross—small cross” for roots of tomato and corn; 60%~70% root concentrates in 0~30cm soil, and the quantity of total roots and the roots in 0~30cm soil are all increasing with the soil water, whatever root length density, root surface area density, root volume density and root weight density, yet there is the inverse for root distribution in 40~100cm soil. The cumulative root distribution curves show that the root grows down with the soil water increase and the root grows to the district among crops with crop growth except for corn in the last stage. The root distribution is large variation in different growth periods, and the soil water is also main factor to influence root distribution in strip intercropping field.