Abstract: The diaphragm wall of "Two walls in one" as a support method for deep foundation pits is increasingly widely used. When it use as supporting structure, its vertical bearing capacity should be predicated and calculated. Taking an excavation in Wuhan project as an example, combining the field monitoring results of static load tests are combined with the post-settlement calculation method of main structures to analyzed the vertical ultimate bearing capacity of the diaphragm wall, and the size effect coefficient is calculated and selected. The proposed method can be used for design of similar excavationsand foundations.