Abstract: This paper presents the results of a great deal of tests, which show that the impervious soil materials for the core wall of the dam of “635” water control project are either nondispersive soil or transitional soil. The paper also includes analytical results of the potential dispersive property of the soil materials of the dam through multipleoptional modification tests, these analytical results provide comprehensive and reliable references for use of dispersive soil materials in construction of water control project.