High slope and unsymmetrical pressure are the key points to tunnel portal excavation of municipal highway tunnel in complex environment. The ear wall arch support structure for portal excavation of unsymmetrically pressured tunnel is studied and optimized. A composite arch support system is established by setting arch support platform foundation and anchor bolt reinforcement at slope foot. The side drift excavation method is adopted in tunnel. The application of ear wall arch support technology to portal of West Line of Huxingshan Tunnel on Zhaoshan Road shows that the abovementioned support technology can guarantee the construction schedule and safety. 