The effect of geocell on the performance of ordinary subgrade is significant, but the improvement of the bearing capacity of subgrade by adding geocell to the high fill subgrade with two side retaining walls is not clear. To explore the application of the geocell in this structure and mechanical characteristics of geocells between different layers and retaining walls, three different reinforcement spacings and one unreinforced operating condition are set to model test. The results show that: In addition to the significant influence of reinforcement on bearing capacity, it also greatly improves the initial modulus of subgrade. When the allowable load is reached, it can still maintain the integrity of the structure itself.The tensile stress of reinforcement is inversely proportional to the depth. The tensile stress and the lifting rate of the first layer are much greater than those of the other layers.The stress distribution of retaining wall is triangular and increases suddenly at 0.22H.