When treating sand layer as a bearing layer, it is regarded as a non-cohesive soil with zero cohesion. This neglect of cohesive force is too low to estimate the strength of the soil, which may lead to relatively conservative design parameters and high engineering cost. In addition, when soil nailing is used in the foundation pit of the sand layer, the hole is not easy to form, and it is easy to collapse and cannot be properly constructed. By introducing the cohesive force of unsaturated sand, In this paper, the mechanical method is used to analyze the stability of the sand layer. The stress field and displacement field redistributed after the hole-forming are obtained., Based on the foundation pit support project of a building in Xi'an, the pore stability is analyzed by numerical simulation software Flac3D. The results show that the pore-forming property of sand-soil layer is related to the clay-like cohesive force. Under a certain degree of compactness, the cohesive force of sand is related to its water content. In the engineering practice, the soil nailing of the sand layer can be ensured by changing the moisture content of the sand.