Abstract: In order to simulate the complex erosion to the overflow structure induced by cavitation and abrasion, a new experimental method was proposed. Based on the characteristics of the Venturi cavitation generator and hydraulic Bernoulli principle, an automatic sand mixed device was invented for high pressure and high speed flow. A series of tests were carried out to investigate the combined action of cavitation erosion and abrasion on hydraulic concrete using this experimental device, and the mechanism of the coupled action of them was investigated. The results show that the wear of the concrete surface had the combined characteristics of the cavitation erosion and abrasion under the combined action. The damage degree of the concrete surface under the combined action was more severe than that under the single action. It was confirmed that promotion and enhancement between the cavitation erosion and abrasion existed in the high speed sand mixed flow. Holes and skeleton structure that formed on the material surface under the impact of cavitation erosion would be worn quickly under the abrasion of sands. Therefore, cavitation erosion made the abrasion much easier.