The invention discloses a device for avoiding a petroleum oil surface being in contact with air. The device comprises an oil drum, wherein an installation cylinder is arranged in the oil drum; one end of the installation cylinder penetrates the bottom of the oil drum and the other end of the installation cylinder is towards the end cover of the oil drum; an oil covering disc is sleeved on one end, which is close to the end cover, of the installation cylinder; sealing devices are arranged between the oil covering disc and the installation cylinder as well as between the oil covering disc and the inner wall of the oil drum to seal; a driving cylinder is arranged on one end, which is far away from the bottom of the oil drum, of the oil covering disc; a center hole of the driving cylinder is a threaded hole; a screw rod is arranged in the installation cylinder; a motor is connected on one end, which is close to the bottom of the oil drum, of the screw rod; the driving cylinder is in threaded connection with the other end of the screw rod; an oil pumping hole parallel to the axis of the oil drum is formed in the oil covering disc; a stopper is arranged in the oil pumping hole. According to the device, a motor is started to rotate the screw rod; one end, which is close to the oil liquid, of the oil covering disc is kept in a state of being in contact with the oil liquid surface; the air is avoided entering the oil drum; and therefore, the volatilization of petroleum is avoided and the waste of petroleum energy is avoided.