The invention provides a device for preventing blow-by oxidation of an optical fiber wire drawing furnace. The device comprises an air pressure measuring device, a processing control device, a sealing device on the wire drawing furnace, and a columnar cavity formed in an extending tube of the wire drawing furnace. The air pressure measuring device is communicated with the columnar cavity through an air tube. A wire drawing tower control system arranged on the wire drawing furnace is connected with the air pressure measuring device and a processing control unit. The processing control unit is further connected with the air pressure measuring device. When the sealing state of the wire drawing furnace becomes poor and the air pressure value in the columnar cavity becomes low accordingly, the processing control unit can be triggered to give out an alarm, the problem that production workers cannot interfere a sealing device in time when the optical fiber wire drawing furnace just begins to blowing gas or the production workers frequently interfere the sealing device to prevent optical fiber wire drawing furnace from blowing gas, and consequently efficiency is low is solved, the losses that due to blow-by oxidation, the strength and quality of optical fibers are reduced, and raw materials are consumed are reduced, and the production qualified rate of the optical fibers is increased.