Embodiments of the present invention provide a security protection method and apparatus for performing security protection during service interruption occurring in a switch network. In an embodiment of the present invention, a transmitting-end device selects each sub-route from a plurality of sub-routes one by one to transmit a call to an opposite-end device; when a trunk device receives the call, it analyzes a route condition from the current selected sub-route to an opposite-end device; the trunk device determines whether to transmit the call to the opposite-end device or report a blocking message to the transmitting-end device according to the route condition; if the transmitting-end device receives the blocking message, then the transmitting-end device excludes the current selected sub-route, judges whether all the sub-routes are excluded, and determines whether to continue selecting a next sub-route or end selecting the sub-routes according to the judgment result.