In order to improve the utilization rate of coal gangue and reduce the harm caused by coal gangue accumulation, the feasibility of using coal gangue as filler in reinforced soil retaining wall projects and the influence of different reinforcement parameters on retaining walls were explored. Through model tests, the stress and deformation laws of retaining walls under different reinforcement lengths (0.66H, 0.99H, 1.31H, where H is the wall height) and different reinforcement strengths (10 kN/m, 20 kN/m, 30 kN/m) were studied. The results show that when the retaining wall is subjected to a load, the deformation of wall surface increases gradually from bottom to top, while the vertical additional stress and the reinforcement strain show a unimodal distribution, with the peak point located directly below the load. Increasing the reinforcement length has a significant effect on limiting the lateral displacement of wall surface and the settlement at the top of the wall. Increasing the reinforcement strength is conducive to enhancing the diffusion effect of the vertical stress. Overall, under a vertical load of 70 kPa, the maximum displacement of wall surface of the geogrid-reinforced coal gangue retaining wall is 0.1%H, the settlement at the top of the wall is 0.27%H to 0.45%H, and the reinforcement strain is less than 0.12%, where the geogrid and the coal gangue achieves a good interaction, and the whole wall is in a stable state. In practical engineering, it is recommended that the length of the reinforcement be no less than 0.5H.