According to structural features of Three Gorges Project(TGP) cofferdam Ⅱ,techn ical indices of materials used for impervious core wall are presented. Through s electing and optimizing,the mix proportion of plastic concrete for core wall was recommended.Triaxial shear tests and stressstrain behaviour analysis were carr i ed out on this material.In addition,laboratory study and insitu monitoring res ults concluded that the properties of plastic concrete achieved all design requi r ements.Normal operation over one year proved the plastic concrete cutoff wall being safe.