The waterconveyance tunnel under study has doublelayer lining structure, with each layer of lining undertaking the loads independently. The seepage water of the tunnel is drained along the tunnel towards outside. After the tunnel has been put into trial operation, it is found that the volume of the seepage water is large, which may increase the operation cost and may jeopardize the safety of the tunnel structure. Therefore, polyurea spraying is made for the circumferential joints and anchorage slots of the tunnel so as to control the water seepage. In the paper, the polyurea material, the prime coating material, the process and technical requirements of the polyurea spraying are presented in detail. Water pressure test is made to measure the bonding strength and thickness of the polyurea layer, which shows that polyurea spraying can achieve good effects. In the end, due to the polyurea spraying, the volume of the seepage water of the tunnel has been reduced significantly.