Disclosed in an embodiment of the present application is a signal transmission device, comprising a first TX, a second TX, a first RX, and a second RX. The first TX is used to send a first transmission signal to an antenna when receiving the first transmission signal; and the second TX is used to send a second transmission signal to the antenna when receiving the second transmission signal. The first RX is used to filter a to-be-transmitted signal to obtain a first reception signal when receiving the to-be-transmitted signal, and send the first reception signal to a first base station transceiver; and the second RX is used to filter the to-be-transmitted signal to obtain a second reception signal when receiving the to-be-transmitted signal, and send the second reception signal to a second base station transceiver. Also provided in the present application are a signal transmission method and system. The present application can transmit signals of multiple frequency bands, thereby reducing the deployment of new sites, and eliminate the need for a 3dB bridge, a different frequency combiner, and a jumper, thereby reducing power loss and improving network performance.