Abstract: The seepage failure characteristics of rock mass in dam foundation relate to the safety of dam operation. There is a very serious seepage failure problem in Xiangjiaba Hydropower Project because of the existence of broken rock mass zone. Through the routine and improved methods for seepage failure, tests on seepage failure characteristics of broken rock mass in dam foundation at the left bank of Xiangjiaba Hydropower Project are conducted. The seepage failure characteristics of broken rock mass are deeply studied based on three different types of test methods. The results indicate that the value of the critical hydraulic gradient of broken rock mass in this project depends on the disturbing degree of rock mass. The larger the disturbing degree, the smaller the value of the critical hydraulic gradient. After the analysis of the reasons for the difference of the critical hydraulic gradient, the rational value of the critical hydraulic gradient for different stress states is proposed.