Partial discharge is an important content of insulation monitoring of high-voltage power equipment, which generates high-frequency signals and real-time monitoring data is of great quantity. Simultaneous detection of multi-channel signals faces technical difficulty, and of high cost and poor reliability, it can also cause unnecessary waste of resources. In accordance with the characteristics and needs of partial discharge monitoring system at substation site, the concept of time-division multiplexing technology in communication technology is adopted into the multi-channel signal acquisition and measuring system, which using multiplexer MAX4638 and virtual instrument. The designed multiplexer for the partial discharge monitoring overcame several shortcomings, such as hardware resources consumption, poor reliability and high cost in multi-channel synchronous acquisition. By using of polling method to achieve one detection device for the time-sharing acquisition and processing of multiple devices or signals, this device can greatly enhance the on-line monitoring system economically and practically in the field application.