The invention discloses a method and a device for a signal distribution system shared by a plurality of communication networks, which include the following main contents: after a communication network with the weakest capability is used for determining the number of antenna points, a communication network with the strongest capability is not directly arranged in the signal distribution system; instead, the power matching relation between other communication networks and the communication network with the strongest capability in the signal distribution system is designed according to parameters such as signal source power, path loss difference value, and difference value of transmitting power at antenna points; after equivalence points of other communication networks for being connected to the signal distribution system are found, the communication network with the strongest capability is connected to the signal distribution system; finally, other communication networks and the communication network with the strongest capability are combined. Therefore, the method and the device for the signal distribution system shared by the plurality of communication networks resolve the problem that manual regulation of the signal distribution system causes heavy regulation workload. In addition, by the adoption of the scheme, reasonable connection equivalence points of other communication networks are worked out, and links between combined communication networks are coordinated.