Abstract: In order to study reasonable test methods for soluble salt in saline soil in highway engineering, the statistical analysis of particle composition in the typical region, the research on preparation particle diameter of coarse grained saline soil and the analysis on relation between soil-water ratio and salt content are performed. The results show that the test method for soluble salt in gravel saline soil using drying soil samples of 300 g which pass 5 mm mesh, the test method for soluble salt in sand saline soil using drying soil samples of 300 g which pass 1 mm mesh as well as the test method for soluble salt in fine grained saline soil using drying soil samples of 100 g which pass 1 mm mesh are representative, and they agree with the actual situations.