Abstract: In this paper systematic study has been conducted on the cementation chdracteritics of a typical red clay based on discussion of the method to determine the content of iron with effective cementation. As can be seen from the result,only a portion of the free iron oxide plays a role in cementation, and the content of iron can be measured by the kinetic chemical selective dissolution,The eresion of the iron with effective cementation will affect signifi-cantly the engineering propertles of the red clay.