To explore the variation laws of horizontal displacement of foundation pit retaining piles and surface settlement outside the pit under finite soil conditions, an excavation model test was carried out on a foundation pit with semi-infinite soil mass on one side and finite soil on the other three sides. The variation laws of internal force, deformation of retaining piles and surface settlement outside the pit under the condition of limited soil mass were obtained and the relationship between the horizontal displacement of retaining piles and surface settlement was further analyzed. The results show that the horizontal displacement of retaining piles is positively correlated with the soil width B, and the reduction of soil width can effectively reduce the horizontal displacement at the top and along the body of retaining piles; the maximum surface settlement increases first and then decreases with the increase of soil width B. Under the condition of limited soil width, the soil width has a significant influence on the surface settlement outside the foundation pit, and there is a critical value of soil width B; the maximum bending moment of the retaining pile body is positively correlated with the soil width B, and the soil width has a small influence on the position of the maximum bending moment. The research can provide theoretical basis and basis for the design and construction of limited soil foundation pit in the future.