The invention proposes that the digital signals out of base band take multiplexing and anti-multiplexing in the passive optical network, and complete multi-user and multi-institution heavy load usingthe method of add-drop multiplexing. It proposes to use software radio technology to achieve more institutional widening module reuse, and realize to reduce the costs of equipment and site. It provides wireless access method and system supporting the multi-user and multi-system, and the system includes: the first add-drop multiplexer, optical line terminal, optical network unit, the second add-drop multiplexer, the widening base stations of different systems.