Abstract: The seepage failure problem of coarse grained soils with cohesive particles is one of the important issues in hydro-electric engineering. For the coarse grained soils with cohesive particles, the content of cohesive particles, particle size distribution and stress state are the most important factors affecting the characteristics of seepage failure. To explore the influence of stress state on the characteristics and critical hydraulic gradient of seepage failure of the coarse grained soils with cohesive particles, seepage failure experiments on some samples of coarse grained soils with cohesive particles are performed. During the experimental process, the vertical stresses of 0.1, 0.3, 0.6 and 0.9 MPa are exerted on the top of the soil samples by using a loading system. The results indicate that the type of seepage failure of the coarse grained soils with cohesive particles is determined by the content of cohesive particle under different stress states. The larger the added stress value is, the higher the critical hydraulic gradient of the soils will be. Based on the evolution process of coefficient of permeability during the experiment of seepage failure process, a new method is proposed for the determination of the critical hydraulic gradient by use of the relation curve of coefficient of permeability and test hydraulic gradient. .