The invention discloses an automatic oil gun, and belongs to the field of liquefied automatic oil guns. The automatic oil gun consists of a spray head, a pressurized gas tube and an oil spray tube, wherein the pressurized gas tube passes through the oil spray tube; the oil spray tube is connected with the spray head; the oil spray tube defines an expanded cavity; a first horn ring is formed on theend part of the pressurized gas tube; the first horn ring is connected with one side of the cavity; a second horn ring is formed at the other side of the cavity; the second horn ring is connected with the spray head; and vent holes which are uniformly distributed are formed in the first horn ring. The automatic oil gun has the beneficial effects that the gasifying effect is good, combustion is sufficient, pollution is effectively avoided, black smoke is not liable to generate, the service life is long, and automatic control can be realized.