Abstract: In view of problem that power quality is influenced by factors of short circuit, open circuit, leakage and harmonics, a monitoring system of power quality with multifunction based on DSP was designed. Design of three parts of the system namely front signal collection circuit, lower computer and analyzing software of upper computer were introduced in details. The experiment result showed that the system can real-timely detect and calculate power parameters of voltage, current, power, power factor, frequency and harmonics and it has better monitoring effect.