Abstract: In the design of foundation pit support in expansive soil area, the conventional pile anchor support system is greatly limited. This paper takes a deep foundation pit supporting project in expansive soil area of Chengdu as an example,according to the characteristics of this project, considering safety, economy, efficiency, environmental protection and other factors, the mechanical expansion anchor pulling pile retaining structure is finally determined, and the scheme selection, support parameter, calculation and analysis process is described in detail.Finally, the monitoring results of the verification, the new retaining structure can adapt to the special geological conditions of expansive soil good and complex surrounding environment, has excellent popularization value and provide some reference for the construction of similar projects in the future.