The composite supporting technology combining the soil-nailing wall with pile-anchor system was used in a deep foundation pit supporting engineering with excavation depth of 19.7 m in Beijing, and the supporting effect is very good. The typical supporting form was studied by the method of three-dimensional numerical simulation with finite difference, and the result showed the work mode and force mechanism of the soil-nailing wall and force coordination process of slope protection pile and anchor bolt in pile-anchor retaining. Comparative analysis was made on the measured data of foundation pit slope displacement and retaining structure force, which can provide scientific guidance to the development and design of the deep foundation pit composite supporting technology.