A tower mounted amplifier, comprising: a first port, connected to an antenna, and configured to perform signal interaction with the antenna; a first band-pass filter, wherein an input end of the first band-pass filter is connected to the first port, and the first band-pass filter is configured to obtain signals in at least two frequency bands through separation from uplink signals that are sent by the antenna and received by the first port, wherein the uplink signals include coupled uplink signals sent by the antenna and received by the first port, and wherein the first band-pass filter is configured to separate, through filtering, the coupled uplink signals to obtain at least an uplink signal in a first frequency band and an uplink signal in a second frequency band; a first amplifier, wherein an input end of the first amplifier, on which a first switch is disposed, is connected to an output end of the first band-pass filter, and the first amplifier is configured to amplify the uplink signals that are in the at least two frequency bands and that are output by the first band-pass filter; a second band-pass filter, wherein an input end of the second band-pass filter is connected to an output end of the first amplifier, on which a second switch is disposed, and the second band-pass filter is configured to receive the amplified uplink signals that are in the at least two frequency bands and that are output by the first amplifier; and a second port, connected to an output end of the second band-pass filter and a base station, and configured to output, to the base station, the amplified uplink signals that are in the at least two frequency bands and that are output by the second band-pass filter, wherein the tower mounted amplifier further comprises a third band-pass filter, an output end of the third band-pass filter is connected to the first port, an input end of the third band-pass filter is connected to the second port, and the third band-pass filter is configured to: obtain downlink signals in at least two frequency bands through separation from downlink signals that are sent by the base station and received by the second port, and output the downlink signals of the at least two frequency bands to the antenna by using the first port. a first port, connected to an antenna, and configured to perform signal interaction with the antenna; a first band-pass filter, wherein an input end of the first band-pass filter is connected to the first port, and the first band-pass filter is configured to obtain signals in at least two frequency bands through separation from uplink signals that are sent by the antenna and received by the first port, wherein the uplink signals include coupled uplink signals sent by the antenna and received by the first port, and wherein the first band-pass filter is configured to separate, through filtering, the coupled uplink signals to obtain at least an uplink signal in a first frequency band and an uplink signal in a second frequency band; a first amplifier, wherein an input end of the first amplifier, on which a first switch is disposed, is connected to an output end of the first band-pass filter, and the first amplifier is configured to amplify the uplink signals that are in the at least two frequency bands and that are output by the first band-pass filter; a second band-pass filter, wherein an input end of the second band-pass filter is connected to an output end of the first amplifier, on which a second switch is disposed, and the second band-pass filter is configured to receive the amplified uplink signals that are in the at least two frequency bands and that are output by the first amplifier; and a second port, connected to an output end of the second band-pass filter and a base station, and configured to output, to the base station, the amplified uplink signals that are in the at least two frequency bands and that are output by the second band-pass filter, wherein the tower mounted amplifier further comprises a third band-pass filter, an output end of the third band-pass filter is connected to the first port, an input end of the third band-pass filter is connected to the second port, and the third band-pass filter is configured to: obtain downlink signals in at least two frequency bands through separation from downlink signals that are sent by the base station and received by the second port, and output the downlink signals of the at least two frequency bands to the antenna by using the first port.