Abstract: For improving the convenience and accuracy of measurement, design method of a DSP-based measuring instrument for multi-function power network is proposed. The paper discusses operation pattern and interface of C501、C500 and AT93C46 chip. In order to improve measure accuracy, error rectify method based on C500 is adopted. This instrument can measure three-phase current, voltage, power factor, active power, reactive power, apparent power, frequency and energy etc.. The measure accuracy reaches 0.5-level.