The invention discloses a differential coupled communication method applied to a high-speed power line carrier (H-PLC) system. Two medium-voltage couplers directly couple negative (-) and positive (+) electrode differential signals of an H-PLC terminal to power lines of different phases in an H-PLC differential coupled communication way after signal cable connection and impedance matching through a differential coupled connector; signals are transmitted on the two power lines of different phases in the differential coupled communication way; and two carrier signals are equal in amplitudes and reverse in phases. In an H-PLC medium-voltage carrier communication process, the method has the remarkable advantages that the signal quality can be improved effectively, and carrier signals with sufficient strengths still exist on a 10kV circuit within a range of 3 kilometers. Moreover, high strong electromagnetic field interference source resistance is achieved; the interference resistance of the carrier signals is enhanced; and the communication quality of an H-PLC network is improved. Meanwhile, a higher signal-to-noise ratio is achieved, and higher communication performance can be provided, so that the quantity of H-PLC pure relays arranged in the 10kV circuit is reduced, and the construction cost of an H-PLC communication network is lowered.