The invention provides a real-time monitoring method of an optical network unit (ONU) operating state. The method includes that step A, when finding that communication damage or communication outage happens to an ONU, the system sends an alarm and tells related ONU communication damage or communication outage, and step B, when the communication damage or the communication outage is restored, the system sends alarm restoration to tell related ONU communication damage or communication outage restoration. With the real-time monitoring method of the ONU operating state, the operating state of the ONU can be effectively monitored, and the fault position of the ONU can be found and located accurately and timely. The real-time monitoring method of the ONU operating state is convenient to use for timely isolating and restoring faults, ensures the reliable operation of the ONU to the maximum limit to relieve the working intensity of network managers, promotes the working efficiency and ensures the smooth communication of automatic business of distribution networks.