The utility model discloses a vapor automatic separating cylinder for fertilizer making equipment. The vapor automatic separating cylinder comprises a cylinder body, wherein a gas inlet pipeline is connected to the side edge of the cylinder body; an electromagnetic valve is mounted on the gas inlet pipeline; a pressure reducing gas exhaust valve is mounted at the lower end of the cylinder body; a pressure gauge is mounted at the upper end of the cylinder body; the pressure gauge is electrically connected with the electromagnetic valve; a plurality of gas outlet pipelines are also connected with the upper end of the cylinder body; a control valve is also mounted on each gas outlet pipeline; the gas inlet pipeline is connected to a vapor boiler; the plurality of gas outlet pipelines are respectively connected to a granulating device, a carburation device, an urine melting device and the like. According to the utility model, as gas directly enters the cylinder body from the vapor boiler and the plurality of gas outlet pipelines are connected to the cylinder body and connected with all the production equipment, gas can be supplied to all the equipment through a large-sized vapor boiler, so that energy is saved and labor and time are also saved.