Abstract: ZY747 PAG water-based quenching medium was used to replace the traditional 46# engine oil as the crankshaft gas tufftriding cooling medium for enviroment protection. The deformation, fatigue properties of the crankshaft, the hardness of the nitride layer and the production cost were studied, compared with those of the traditional cooling medium. Results show that there was no difference on the fatigue properties of the crankshaft, but could lower the production cost when using this new cooling medium.