Abstract: Based on the data from geological exploration and experiment of some tailings reservoir at home,this paper discusses the granule variational rule of tailings sand on plane and vertical plane,considering that the correlation to the angle of internal friction unde different granularity,water content,void ratio and relative density.The results show that the void ratio and relative density has great influence on the angle of intenal friction,which is irrelative to the deposit depth.In order to improve the stability of tailings dam,the perfect method is suggested to increase the relative density or decrease the void ratio of tailings saind which can be reinforced by geotextile and bear higher cohesion.