The utility model provides a crankcase ventilation structure belongs to locomotive accessory field. It has been solved and has had now under high and cold environment, the frozen problem of the littleload triton passageway of crankcase. This crankcase ventilation structure, the crankcase includes the cylinder head, the valve mechanism cover of setting in the cylinder head, last being provided with of valve mechanism cover is used for receiving the combustion chamber, the oil and gas separator of crankcase waste gas, set up air intake manifold in the cylinder head, be provided with the intakeduct of intercommunication air intake manifold and combustion chamber in the cylinder head, the ventilation structure including set up in valve mechanism cover and with the first passageway of oil andgas separator gas outlet intercommunication, the setting in the cylinder head and with the second channel of intake duct intercommunication, first passageway communicates with the second channel eachother. The utility model discloses whole little load triton passageway is integrated inside gas cylinder head component totally, has avoided little load triton passageway frozen risk in winter totally through the high temperature heat -conduction of cylinder head during operation, and the while is the cost is reduced also, has improved the operational reliability of engine.