A new method of calibration signal implementation for power quality monitoring devices based on heterogeneous equivalence of similarity theory is proposed in the paper. Timing-shift similarity calculation between the sampling signal sequence of the monitoring device and the output signal sequence of standard source is carried out, to analyze calibration signal synchronization method and its composition. Output method of heterogeneous calibration signal in the case of the whole point sampling and random sampling of the monitoring device is studied. In addition, the calibration software about power quality monitoring devices is developed to measure accuracy of the devices, and the calibration results show that the questions of asynchronous between the sampling signal of the monitoring device and the output signal of standard source, and mutual interference between adjacent calibration signals are completely solved. This greatly improves the accuracy and reliability of detecting the monitoring device, improves the level of monitoring grid and user power quality, and has played a positive role in upgrading and promoting the technology and industrial development of power quality monitoring devices.