Organic phosphates are widely used as additives in lubricating oils and water-based lubricants because of their good lubricating property.Water soluble polyethylene glycol(400)ester of phosphate was synthesized with raw materials of P2O5 and polyethylene glycol(400)by sustained release method,and its extreme pressure and antiwear performance of polyethylene glycol(400)ester of phosphate was researched.The result shows that polyethylene glycol(400)ester of phosphate can significantly improve the extreme pressure and antiwear performance of the water based lubricant.The water-based lubricant with polyethylene glycol(400)ester of phosphate as additive has good corrosion performance of Cu.