The invention provides an operation vehicle. The operation vehicle comprises an engine, a waste gas purifying device, a reductant box, an engine cooling water return, a branch route, a valve, a receiving part, and a valve control part. The waste gas purifying device is used to purify the waste gas discharged from the engine so as to remove the nitrogen oxides. The reductant box is used to store the reductant which is supplied to the waste gas purifying device. The engine cooling water return comprises a water pump, and the water pump is driven by the engine so as to make the cooling water repeatedly circle in the circulation route. The branch route is arranged so as to carry out heat exchange between the cooling water and the reductant in the reductant box. The valve is used to control the supply of cooling water to the branch route. The receiving part is used to receive the operation command from an operator. The valve control part is used to control the valve according to the operation command from the operator.