Abstract: This paper provides the investigation results of the durability and the defects occurring in 70 mass concrete constructions in china. The defects of mass concrete gates and dams are summarized as follows: 1. crack damage; 2. leakage and leaching corrosion; 3. freeze-thaw erosion; 4. scouring and wearing; 5. reinforcement corrosion; 6. corrosion of surrounding water. All these defects are illustrated by typical constructions. For improving the durability of hydraulic concrete structures, some useful recommendations are given.