The invention provides a sealing device for a guide vane sleeve of a water turbine. The sealing device comprises an annular sealing part, a pressing cover and a connecting part, wherein the annular sealing part closely sleeves the guide vane sleeve, and the bottom surface of the annular sealing part is propped to the upper surface of a top cover; the pressing cover consisting of a base barrel and a connecting part sleeves the guide vane sleeve; the connecting part is connected with the top cover through a connector; the surface of the bottom prat of the base barrel is pressed to be propped to the annular sealing part under a state that the connector is connected with the top cover. According to the sealing device for the guide vane sleeve of the water turbine, the annular sealing part and the guide vane sleeve are sealed, and the annular sealing part and the top cover are sealed, so that a gap between the guide vane sleeve and the top cover can be effectively sealed, and as a result, water permeating can be prevented; in addition, the sealing device for the guide vane sleeve of the water turbine has the advantages of being simple in structure, and convenient to dismount and mount; the guide vane sleeve and the top cover are prevented from being dismounted during mounting, maintaining and replacing, so that both manpower and time can be saved to the maximum.