Abstract: A kind of chemicals was synthesized by the authors,and it is added in expansive soil with different proportion.These specimen made of expansive soil improved by chemicals are cured and then submerged under water in a container.unconfined compression and direct shear tests are carried out,and the tests indicate that stability and strength of expansive soil improved by chemicals and submerged are better and greater than those of the original expansive soil submerged respectively.The test results are useful to engineering practice.