Abstract：Presently，the researches for differentiation and grade criterion of intense swelling soft rock are in primary phase with important application in practical engineering. On the basis of previous achievement，this paper presents the most essential matter of soft rock with strong swelling characteristics by combining engineering practice，field and laboratory experimentation results. The reason of strong swelling characteristics is that the soft rock contains plentiful high hydrophilicity clay mineral，such as illite / montmorillonite mixed-layer mineral. At the same time，the differentiation and grade criterion of strong swelling soft rock by combining physics，chemistry and mechanical index are fully discussed and the results prove to be successfully in the engineering practices.
