The anti-wear,friction reducing and extreme pressure properties of three types of waterbased lubricants frequently used in synthetic grinding fluid such as polyethers,phosphate esters and polyesters were researched.The effects of three types of lubricants on the antirust and hard water resistance of synthetic grinding fluid were investigated.The results demonstrate that polyethers have excellent anti-wear property but poor extreme pressure,phosphate esters have good extreme pressure property but common anti-wear property,while polyesters have outstanding anti-wear and extreme pressure properties.Polyethers have good hard water resistance,while phosphate esters and polyesters have poor hard water resistance.Polyethers and polyesters have no effect on the antirust of the synthetic grinding fluid,while phosphate esters have a corrosive effect on cast iron.