The invention relates to a modifying agent for sealing oil of air cabinets in steel enterprises, which comprises by weight the following components: poly alpha-olefin 3-8 portions; alkene succinic acid 1-6 portions; ammonia and epoxy ethane condensation compound 1-4 portions; ethylene propylene copolymer thickener 2-10 portions; and basic oil for lubricant 72-93 portions. With the invention, 1. the anti-rust and anti-corrosion performance of the sealing oil is improved, the anti-corrosion and anti-rust capability of such places as the wall plates, piston springs and sealing mechanisms of aircabinets are guaranteed, and the safe running of the air cabinets are guaranteed; 2. the anti-emulsion capacity of the sealing oil is improved, which avoids the sealing oil from running with water; 3.on-line modification is carried out during the operation of the air cabinets. The invention can additionally saves energy, avoid any discharging of degraded oil, drop efficiently any pollution on theatmosphere and water environment, save effectively the labor from the users, prolong the overhaul period of the air cabinets and the service life of the sealing oil.