A multi-mode base station and a method for sending/receiving signals thereof are provided. In the base station, each base-band single-board is connected to a corresponding radio frequency (RF) unit through a multi-mode exchange bus, and the base-band single-boards of different modes are intermixed by using the compatibility of the exchange bus with in-phase/quadrature (IQ) data of various modes. Synchronization information, such as frame numbers required by various modes, forms a synchronization burst through multiplexed framing. Meanwhile, by using the same system clock, the synchronization burst and system clock are transmitted to the base-band single-boards of various modes through a set of synchronization clock buses. The main control and transmission functions are uniformly provided for each base-band single-board in the base station by a shared common module. The filling and synchronization of wireless IQ data of various modes are realized according to common-multiple relation mapping.