The invention provides a passive optical network session service controlling method and an optical line terminal. The passive optical network session service controlling method comprises the following steps that: the optical line terminal receives a session call request which comprises a called terminal equipment identifier and is transmitted by calling terminal equipment; the optical line terminal judges whether the called terminal equipment is subordinate terminal equipment of the optical line terminal according to the called terminal equipment identifier; if the called terminal equipment is the subordinate terminal equipment of the optical line terminal, the optical line terminal transmits the session call request to the called terminal equipment; the optical line terminal receives a call response message fed back by the called terminal equipment; and the optical line terminal establishes a media stream transmitting channel between the calling terminal equipment and the called terminal equipment. By the method and the optical line terminal, session service backup can be provided for a passive optical network, and the load of a core network is reduced.