The invention provides a travelling crane for oil tank construction in a cave depot. The travelling crane comprises an annular guide rail, wherein a central column is installed in the circle center of the annular guide rail, the top end of the central column is connected with one end of a girder, the girder can rotate around the central column, the other end of the girder is connected with a movable column, an electric chain block is installed on the girder and can move along a slide way which is arranged on the girder, a support seat is installed on the bottom end of the movable column, a hollow cavity is formed in the support seat, a wheel seat is installed in the hollow cavity, a first idler wheel and a second idler wheel are installed at the bottom of the wheel seat and are matched with the annular guide rail, a hydraulic cylinder is installed between the top of the wheel seat and the top surface of the hollow cavity, a hydraulic motor is installed on the wheel seat, an output shaft of the hydraulic motor is connected with a rotating shaft of the first idler wheel through a transmission device, and each of pipelines of the hydraulic cylinder and the hydraulic motor are connected with a hydraulic pump through solenoid valves. The travelling crane can be used for substituting for manpower to transport and hoist weights in the oil tank assembling or maintaining process, is stable in structure and convenient to erect, and has high safety.