The present invention discloses a link scanning method for cascaded RCUs and a remote electrical tilt antenna system. The method includes: receiving, a link scanning message and sending the link scanning message to the RCU in the next cascaded RCU; generating, a link scanning response message, sending the link scanning response message to the RCU in the preceding cascaded RCU, and reporting the link scanning response message to the CCU, and sending, the link scanning message to the CCU. In the present invention, by adding a time delay in the link of the remote end serial communication bus, each RCU does not respond to the link scanning message simultaneously, the time-delayed link scanning response messages in the link of the remote end serial communication bus of each RCU are not aliased, therefore, the bus conflict problem of the link scanning when the RCUs are cascaded is effectively solved.