The efforts to improve automatic transmission (AT) efficiency for vehicle fuel economy are constantly continuing. In an AT the oil pump is the largest power loss factor. Therefore the effect on fuel economy is very high. The AT oil pump system has structural contradictions (high pressure × high flow), and the efforts to improve these areas are concentrated.In this paper, a two oil pumping system was designed to improve the efficiency and performance of a 6 speed AT installed in a Hybrid Electric Vehicle (HEV) , and the improvement was confirmed by a prototype experiment. As a result of the experiment, two pumping system was shown to improve vehicle fuel economy while reducing noise and oil pressure vibration.