Abstract: Sichuan power transmission lines pass through the mountain area with a wide distribution of gravel soil. The gravel soil is a special rock and soil between the rock body and the soil body. There are different types of the gravel soil classification. For the gravel soil foundation pile under horizontal with different stone content, the horizontal bearing characteristics have a big difference. The current standards give a quite wide range of the proportional coefficient m of ground horizontal resistance coefficient. In practical application, we evaluate the m value too random. At present, there are some researches on the soil properties of gravel soil with different stone content, however, there are few researches on the characteristics of pile-soil horizontal interaction for gravelly soils with different stone content. Therefore, evaluating the characteristics of pile-soil horizontal interaction and m value on the gravel soil foundation under different stone content is a task to be resolved for the design of transmission tower pile foundation. In this paper, single pile static lateral loading tests are conducted in State Key Laboratory of Geohazard Prevention and Geoenvironment Protection of Chengdu University of Technology. We obtained three gravel soil with different stone content by conducting sizing test. We carried out three sets of physical simulation tests with different stone contents respectively, and obtained the mechanical parameters of gravelly soil with different stone contents. Then we got the effects of the displacement of pile top, the internal force of the pile, the proportional coefficient m of ground horizontal resistance coefficient with different stone content. We got the variation tendency of the m value with different stone contents. According to comparative analysis, we got the experiment characteristics and laws, and studied the bending moment value of pile curve, shear force curve, soil pressure curve on the pile side, and the variation tendency of the m value with different stone contents. The results indicate that pile bending moment first increases and then decreases from pile top to pile bottom. As the stone content of the gravel soil foundation grows, the maximum bending moment value of pile grows nonlinearity. The maximum bending moment value is buried approximately at 0.3 meter depth location of the section. At the condition of high stone content, bending stiffness can be properly increased at the position of the section at design time. As horizontal force increases, soil pressure on the pile is nonlinearly increase, too. As the stone content of the gravel soil foundation grows, the ground horizontal resistance increases, the position of zero of soil pressure on the pile side can also improve. This is due to the improvement of the horizontal resistance of the gravel soil and the simultaneous increase of the earth pressure before and after the pile. The stone content increase every 10%, the m value would also increase about 1.15~1.40 times. This research fill the application blank which does not address the different stone contents of the gravel soil affecting m value. It can also be used as a reference of the proportional coefficient m of ground horizontal resistance coefficient.