Abstract: In order to greatly prolong the checking period of pumps for the eccentric-wear oil wells in the medium and high water-cut periods,a water-based lubricating fluid FYR-4 has been synthesized based on the water-based lubrication theory widely applied in the fields,such as mechanical cutting,grinding,drawing,rolling and hydraulic transmission.The water-based lubricating fluid FYR-4 takes polyoxyethylene glyceryl borate stearate,fatty acid imidazoline borate,amphoteric surfactant SS-Z,and polyoxyethylene alkyl phenol ether sulfonic aicd sodium as main agents,and with synergistic function of fluorocarbon surfactant and vitamin C,jointly forming chemical reaction film and adsorption film with boundary lubricant on the surface of tubing pipe and sucker rod.The adsorption film and tribochemical reaction film were formed by highly reactive phosphor and nitrogen,functioning as carrier fatty acid molecule in the system with good friction-reduction and biodegradability.By adding FYR-4 water-based lubricating fluid of 0.25%-0.50% to 30 oil wells for routine maintenance,their average checking period of pumps has prolonged by 275 days or even longer,providing valuable reference for the eccentric-wear management of oil wells in medium and high water-cut period.