A new roller compacted concrete dam of Fengman Hydropower Station is to be built in the toe of the old dam,which was identified as a dangerous dam.The new dam during construction would be influenced by the high-speed flow discharged from the old dam,which is an important problem to be considered for the first time in China,and which would affect the construction of the whole project.Therefore,a series of erosion experiments were conducted in this article.A high-speed flow erosion test apparatus was developed for the erosion experiments of the new dam materials.The maximum jet velocity goes up to 40 m/s and the section area of the nozzle is 0.0025 m2.In the process of experiments,the equipment shows a good performance.Erosive wear tests for two types of materials used in the new dam,a roller compacted concrete and a distorted concrete with four kinds of ages were carried out with the flow velocity in the range of 30 m/s-35 m/s.Erosion parameters and erosion laws for the two types of concretes with different ages were determined,and a general relationship between the erosion rate and the flow velocity is obtained as:,with the velocity exponent between 3.33 and 3.93.It is concluded that the erosion resistance of the distorted concrete is better than that of the roller compacted concrete and the mechanical properties of the concretes of over 14 d age are influenced slightly by the water impact.The test results might serve as a practical technique guide for the safety of this project during its construction in the flood season. A new roller compacted concrete dam of Fengman Hydropower Station is to be built in the toe of the old dam, which was identified as a dangerous dam. The new dam during construction would be influenced by the high-speed flow discharged from the old dam, which is an important problem to be considered for the first time in China, and which would affect the construction of the whole project.Therefore, a series of erosion experiments were conducted in this article. A high-speed flow erosion test apparatus was developed for the erosion experiments of the new dam materials. maximum jet velocity goes up to 40 m / s and the section area of ​​the nozzle is 0.0025 m2.In the process of experiments, the equipment shows a good performance. of materials used in the new dam, a roller compacted concrete and a distorted concrete with four kinds of ages were carried out with the flow velocity in the range of 30 m / s-35 m / s. Erosion parameters and erosion laws for the two types of con cretes with different ages were determined, and a general relationship between the erosion rate and the flow velocity is obtained as:, with the velocity exponent between 3.33 and 3.93. It is said that the erosion resistance of the distorted concrete is better than that of the roller compacted concrete and the mechanical properties of the concretes of over 14 d age are alia slightly by the water impact. the test results might serve as a practical technique guide for the safety of this project during its construction in the flood season.