Power quality is an important index of the electrical industry, and it affects the interests of both power utilities and customers. This paper introduces the functions and methods of power quality monitoring, and it discusses the importance of on-line monitoring for power quality management. Then the paper focuses on the demand for the communication network of power quality on-line monitoring system, and it analyzes the performance of different communication networks of power quality on-line monitoring system, and OPNET simulator is used to validate the analysis. Result shows a shared 10M Ethernet couldn't fulfill the demand of power quality on-line monitoring, and a switched 10M Ethernet or better is required.