About half input power of general hydraulic power transmission system will be changed into heat energy and lost. Therefore low energy consumption with high efficiency is a very important target to evaluate a hydraulic system. The work principle of a new double-acting pneumatic-hydraulic pressure amplifier with three level pressure output was introduced which was designed based on the idea of energy saving and pro-environment. Its running characteristic was analyzed and its main parameters were calculated. A detail analysis on how to maintain power and increase use-life was made.