The invention discloses a transmission system of electric energy quality on-line monitoring data. The transmission system comprises a monitoring device, a router and a server. The monitoring device comprises a data collecting device and a first wireless communication device. The server comprises a second wireless communication device and a processor. According to the transmission system of the electric energy quality on-line monitoring data, the monitoring device is provided with the first wireless communication device, after the data collecting device obtains source monitoring data, the first wireless communication device sends the source monitoring data to the server of the second wireless communication device through the router, and the purpose that a wireless network is used for transmitting the electric energy quality on-line monitoring data is achieved. The monitoring data are transmitted through the wireless network, transmission speed is high, and line setting is lowered. In addition, for data transmission, a virtual private network (VPN) is established on the wireless network through a layer two tunnel protocol (L2TP), interference from outside is avoided, and cost is low.