The present disclosure provides a method, device and system for implementing emergency call override service; wherein the implementation method comprise: a first application server (AS) on a called side receives an initial request message, carrying a service identifier indicating an emergency call override service, from a second AS on a calling side; and the first AS implements the emergency call override service according to the service identifier. In the IMS network architecture, by adding a service identifier, indicating emergency call override service, in an initial request message based on SIP, an AS network element on a called side can implement emergency call override service according to the service identifier, thereby solving the problem that the emergency call override service cannot be implemented in the current IMS network architecture.