The rock mass of foundation of Shuibuya Project is a type of stratified sedimentation rock mass composed of interbedded stratum by weak layers and hard layers. For the complexly lithologic composition of stratum unit, well developed shear bands and karst, so it is a difficult issue how to carry out engineering classification of rock mass. In practical engineering, it is not satisfactory in resolving these problems entirely with National Standard for Engineering Classification of Rock Mass（GB50218-94）. Therefore, on the basis of abundant rock mechanical test results and engineering experience, and in combination with the composite characteristics and major controlling factors of Shuibuya Hyro-project, the quality classification of engineering rock mass is put into practice. And the results can provide evidence for engineering design and support of underground cave.