In order to increase the strength of sand, water-soluble polymer was used to improve it. The direct shear test was carried out on the improved sand with different dry density, curing agent content and curing time, and the cohesion and internal friction Angle were analyzed. The results show that the shear strength of sand improved by water-soluble polymer is improved to a certain extent, which is due to the fact that water-soluble polymer strengthens sand samples and forms elastic mucosa wrapped with particles and connected with each other, thus increasing the strength of soil. When the curing time is constant, the shear strength of the improved sand increases with the increase of curing agent content. The maximum cohesion of the sample can reach 183.52 kPa. When the curing agent content is constant, the shear strength of the improved sand increases with the increase of curing time. The maximum cohesion of the sample can reach 200.19 kPa. The shear strength is positively correlated with curing agent content, curing time and dry density of the sample. Elastic mucosa formed by water-soluble polymer solution in sand wraps sand particles and fills sand voids, thus enhancing interaction between soil particles and improving engineering properties of sand.