Power consumption is a vital issue for communication systems, especially for those which powered by batteries. In wireless com-munication system, the power consumption of PA (power amplifier) consumes a large portion of power compared with another component. How to reduce the power consumption of PA is always one of the big topics in the R&D and application of PA. Modern communication systems which have the high Peak to Average Power Ratio (PAPR). Envelope tracking technology can effectively reduce the power consumption of PA, especially for the high PAPR system. In the meantime, ET does not affect the performance of PA and communication system. This paper introduces the principle of ET, and gives the test method of ET performance. An ET test system has been built using R&S SMW 200A vector signal generator and FSW vector signal analyzer. The measurement result shows 20% of power saving by the application of ET.