In order to solve the problems of distribution management and power quality improvement of large electricity users, a new design of power quality intelligent diagnosis instrument based on dual high speed ATmega128L and Zigbee is proposed in this paper, and introduces its hardware interface circuit design, hardware program design and application in power quality, and its feasibility is verified by field test. High precision MAX125 and ATmega128L are used for data synchronous acquisition, calculation, analysis, display, SD card storage and results record, moreover, Zigbee is used for uploading data which are used for the upper system software to make power quality analysis, thus can strengthen electricity management of users, improve power quality and save energy. The instrument has advantages of easy portability, low cost, high precision, strong anti-interference ability and easy to promote, thus can effectively meet the needs of dedicated large users’ power quality managements.