The invention discloses a powder tank truck which comprises a tank body, a manhole and a manhole cover device, wherein the manhole is arranged at the top of the tank body, and the manhole cover device closes the manhole; the manhole cover device comprises a seat body, a cover plate, two driving mechanisms and a control system, wherein the seat body is fixedly connected with the periphery of the manhole, encloses the center of the manhole and is provided with an opening; the cover plate is used for sealing the seat body; the control system is connected with the two driving mechanisms; the cover plate comprises a first part and a second part which are hinged together at one end; the two driving mechanism are connected with the first and second parts of the cover plate respectively; the control system comprises an operation mechanism arranged in a cab of the powder tank truck; and the operation mechanism is controlled so that the two driving mechanism can drive the first and second partsof the cover plate to gather together or leave each other so as to close or open the manhole. The manhole cover device of the powder tank truck can be automatically opened or closed, the labor intensity is reduced, and potential safety hazard is avoided. The cover plate is automatically sealed by use of pressure in the tank body, and better sealing effect is obtained by higher pressure.