By integrating WebRTC technology in HTML5 with IP Multimedia Subsystem (IMS) technology in a mobile network, we have developed a new Urban Integrated Emergency Response System (UIERS), which is more suitable for a modernized city. This system can be widely accessed by a mobile intelligent terminal, such as a smartphone, tablet, PDA, or traditional SIP terminal. Users can log in via a web browser and call up users who are in the IMS/PSTN network directly. Without installing applications or loading a plug-in, this system is much more applicable in different platforms and is more easily upgraded and maintained in Browser/Server (B/S) structure mode.