Labyrinth structure of engine crankcase ventilation system

The invention discloses a labyrinth structure of an engine crankcase ventilation system. The labyrinth structure comprises a ventilation pipe side labyrinth arranged on a cylinder cover, and a PCV (Positive Crankcase Ventilation) valve side labyrinth, and is characterized in that a connecting trough is arranged on a cylinder cover, one end of the connecting trough is communicated with the head end of the ventilation pipe side labyrinth, and the other end of the connecting trough is communicated with the head end of the PCV valve side labyrinth. According to the invention, the connecting trough is arranged between the PCV valve side labyrinth and the ventilation pipe side labyrinth, the pressure in the ventilation pipe side labyrinth is balanced by the PCV valve side labyrinth, so that pressure difference between the ventilation pipe side labyrinth and a crankcase is reduced, engine oil precipitated from the ventilation pipe side labyrinth can successfully flow back to the crankcase, thus reducing the engine oil consumption of an engine; and the labyrinth structure is applicable to crankcase ventilation systems of a gasoline engine, a hybrid engine, a hydrogen fuel engine and the like so as to improve the separation effect of oil and gas mixture.