The invention discloses a medium-voltage broadband power carrier networking system and networking method suitable for distribution automation. Power carrier communication is realized by arranging medium-voltage broadband carrier equipment for distribution equipment connected through a medium-voltage power line in a distribution network respectively; the medium-voltage broadband carrier equipment comprises a medium-voltage broadband carrier modem and a coupler; the data interface end of the medium-voltage broadband carrier modem is connected with the data port of the distribution equipment; the carrier signal interface end of the medium-voltage broadband carrier modem is connected with the coupler through a coaxial cable; and the coupler is coupled with the medium-voltage power line. The medium-voltage broadband power carrier networking system has high interference resistance, a high frequency band utilization ratio, a high communication bandwidth, is used for transmitting in a way of being completely dependent on the power line, and has the advantages of simple structure, easiness in expansion, easiness and convenience in maintenance, safety, reliability, moderate cost and the like. By adopting the medium-voltage broadband power carrier networking system disclosed by the invention, transparent transmission and seamless joint with other system networks in distribution network automation can be realized, and an effective communication way is provided for distribution network automation.