A signal transmission method used in a donor or a service antenna device in a wireless relay station is provided. The signal transmission method comprises receiving a first and a second direction signals by using an antenna and an optical transmission module. Each of a plurality of band filters performs filtering on the first direction signal. A control unit determines a transmission mode of the first signal according to the band of it. The control unit activates one of a plurality of first direction filters and one of a plurality of second direction filters between the antenna and the optical transmission module according to the transmission mode. The first and the second direction signal are transmitted to a remote device and an optical fiber connected device through the antenna and the optical transmission module. A donor antenna device and a service antenna device are disclosed herein as well.