Abstract: When the foundation base of a tunnel lies in soft layers, the bearing capacity of the base is hard to meet the requirements of structural force. To ensure the stability of the tunnel structure, foundation base strengthening design is most important to increase the bearing capacity of the same. Because of the characteristics of root pile which has high bearing capacity and can nimimize the disturbance to the strata of the tunnel barrel in narrow and much limited construction space. The application on root pile of foundation base in loess tunnel is a significative experiment. This paper introduces the instance of new xiaozegou tunnel of Line 2 of Shen-Shuo railways and compares the change regularity of single root pile’s load capacity with different aggregate, different length, different diameter and different reinforcement and recommend the decided method of single root pile’s load capacity in similar layers by loading test in site. It provide scientific foundation to design of root pile in loess and reference to future similarworks.