Embodiments of the present invention provide an antenna apparatus, a base station and a communications system. The antenna apparatus includes: an antenna part, including a common radome; an active part, connected to the antenna part and including at least one active module, where each active module includes at least one antenna element, and an element reflector and a phase shifter and a radio frequency module that are corresponding to each antenna element, where the element reflector of the at least one active module is configured to implement an antenna function; and a common part, connected to the active part and the antenna part, and shared by the at least one active module in the active part, where the common part includes at least one common module. By using the above antenna apparatus, each radio frequency module can be flexibly configured, so as to simplify onsite replacement and maintenance operations.