The utility model provides a gas-oil separation check valve of an automobile crankcase and belongs to the technical field of automobiles. The check valve solves the problem that oil gas of an existing gas-oil separation check valve of the crankcase cannot flow into a gas inlet channel smoothly so that the problem of backflow of fresh mixed gas in a gas inlet pipe occurs when an engine has small load or does not work. The check valve comprises a valve body. A cavity, a gas inlet channel and a gas outlet channel are arranged in the valve body, and the gas inlet channel and the gas outlet channel are communicated with the cavity. A valve core is arranged in the cavity, is flat and can slide along an inner wall of the cavity. A spring is installed at one end of the valve core, one end of the spring acts on a spring seat fixed in the valve body, and the other end of the spring acts on the valve core to enable the valve core to seal the gas inlet channel. The gas-oil separation check valve enables the oil gas to smoothly flow into the gas inlet channel, and backflow of the fresh mixed gas in the gas inlet pipe is avoided when the engine has small load or does not work.