The invention discloses a protective relay coupling network for composite signal transmission. In the network, after a direct current and high-rate data are coupled by utilizing a coupling transformer, a high-voltage alternating current signal is isolated by utilizing a high-voltage relay; a control command is transmitted into a cable for transmitting through the high-voltage relay after passing through the coupling transformer; a received signal is switched by a second high-voltage relay; the high-voltage alternating current signal is loaded to a load end; the direct current and the high-rate data are divided into two paths, wherein one path is transmitted to a data transmitting and command receiving unit through a blocking circuit, the coupling transformer and a third high-voltage relayin turn while the other path is transmitted to a direct current power supply module through a second low-pass filter; and simultaneously, the received signal serves as the control signal of the second high-voltage relay and the third high-voltage relay after low-pass filtering. The protective relay coupling network for the composite signal transmission can effectively improve the transmission reliability of a signal path on the basis of thoroughly isolating high and low-voltage circuits, and ensures the stable coupled transmission of four types of high and low-voltage signals to the maximum.