Taking the deep foundation pit support project of a commercial center in Nanchang as an example, on the premise of ensuring safety, various factors were taken into account to reduce the cost of foundation pit support through analysis of the surrounding environment, geological conditions and excavation depth. In the control of groundwater, water cutting-off was combined with dewatering to control the water table outside the pit at the properly designed elevation. The composite support structure was adopted for foundation pit support with the soil nailing wall and tensional anchor piles used for different parts. Various design alternatives were compared and optimized to attain safety, applicability and proper economics.