The invention provides a cleaning and purifying device used for a hydrodynamic transmission. The cleaning and purifying device comprises the hydrodynamic transmission and an oil adding tank, wherein an oil inlet of the hydrodynamic transmission is connected with the oil adding tank through a rear oil pump, and an oil outlet of the hydrodynamic transmission is connected with a transfer oil tank through a front oil pump. The transfer oil tank is connected with an oil inlet of a purifying device body, and an oil outlet of the purifying device body is connected with the transfer oil tank and the oil adding tank. A first solenoid valve is arranged between the oil outlet of the purifying device body and the transfer oil tank, and a second solenoid valve is arranged between the oil outlet of the purifying device body and the oil adding tank. A liquid level relay is arranged in the transfer oil tank. By carrying out replacement and cleaning on transmission oil in the hydrodynamic transmission, purifying the polluted oil having been subjected to replacement treatment and recycling the oil, the oil is saved, and the environment is protected. The defect that parts of the hydrodynamic transmission are not thorough cleaned before assembling is effectively overcome, and pollution generated in the assembling test process is effectively removed. In this way, performance of the hydrodynamic transmission and the cleanness of a whole-vehicle transmission system are improved.