The invention discloses a ventilating system used for engine cylinder block electroplating. The ventilating system comprises an air draft power device and a backflow part with a ventilating system air inlet channel, when the ventilating system is used, the backflow part is sleeved with a cylinder block and is provided with a backflow channel communicated with a liquid storage tank, and the backflow channel and the air inlet channel share the same channel; an air draft opening of the air draft power device is communicated with an air phase space of the liquid storage tank. Cylinder block electroplating is completed with the ventilating system, the ventilating system can be adaptive to electroplating liquid and cleaning liquid to form a scheme of flowing electroplating outside the tank, ventilation is formed in a targeted mode, volatile steam of the electroplating liquid can be absorbed away thoroughly, it is ensured that the ambient environment is protected in the electroplating process and prevented from being polluted, and therefore physical and psychological health of workers is ensured; meanwhile, draft power formed by the ventilating system is beneficial for liquid backflow, stability of the electroplating environment is ensured, and blocking is avoided.