Abstract: Many oilfield with hydraulic piston pump enter into the middle-high water cut stage in China. Due to the pure crude oil is pressured and heated as ower fluid, the great amount of crude oil with high water cut is produced and economic benefit is very poor. in addition, some equipments have reached fatigue limit and accident possibility is increased because they have been run in high pressure and high temperature for a long time. This paper introduces systmatically the application situation of water base power fluid at home and abroad, and gives a feasibility study on water base power fluid of hydraulic piston pump in China from the advantages of water base power fluid, surface and subsurface match techniques and economic benefit evaluation. It points out the most economic production way for hydraulic piston pump.