The present invention provides an alarm method for a multi-mode base station. The method includes generating, by the multi-mode base station, alarm information in a first operation mode in a first multi-mode operation mode. The multi-mode base station determines that the alarm information is applicable to all operation modes in the first multi-mode operation mode. The multi-mode base station sends the alarm information as public alarm information of the first multi-mode operation mode to a network management system. The present invention further provides a multi-mode base station and a communication system. The present invention is capable of determining a scope of operation modes related to alarm information generated in the multi-mode base station, which is used to manage the alarm information.