This study investigates the leaching test to the dissolution deformation characteristics of gypsum soil along the Baiji railway, the dissolution deformation coefficient and deformation stability time of two types of gypsum soil collected from flat and mountainous areas under different loads are obtained. The test results show that the soluble salt in gypsum soil is the main cause of the collapse and deformation of gypsum soil. The causes of gypsum soil's sagging deformation and the influence of load, salt content and particle gradation on gypsum soil's sagging deformation were discussed. When the external load does not change, the gypsum soil can produce large deformation in a short time after being immersed in water, accounting for more than 80% of the stable deformation, and thereafter can still produce large deformation under the action of long-term leaching. The dissolution deformation of gypsum soil increases with the increase of load. With the extension of the leaching time, the soluble salt content gradually decreases, and the dissolution deformation of gypsum soil tends to be stable with the increase of load. The size of the collapse deformation is related to the salt content of the gypsum soil. Under the same external load, the higher the salt content, the greater the deformation of gypsum soil. The rate of dissolution deformation is mainly related to the particle gradation of the soil. The larger the content of coarse particles in gypsum soil, the faster the dissolution deformation speed.