The new retaining wall structure of cantilever prestressed SMW construction method is a new type of foundation pit support composed of inserting profile steel in the front of the cement soil retaining wall, setting vertical prestressed anchor cable in the back, and setting rigid reinforced concrete cover beam between the two. To clarify the mechanical behavior of this new type of structure, the stress process is analyzed, the reasonable deformation calculation model is explored, and the deformation control measures are taken. The concrete method is to regard the steel-cement soil composite as a whole component, establish the deformation differential equation and boundary conditions, and the deformation calculations are performed using two algorithms: In algorithm 1, its deformation under the action of pretension prestress is calculated; In algorithm 2, the deformation of the section steel top is calculated by the additional bending moment. Taking the whole construction process of a deep foundation pit as an example, the measured statistical analysis results of the retaining wall show that the theoretical deformation values are basically consistent with the monitoring values, while the deformation values calculated by ignoring the mechanical contribution of cement soil and the effect of prestress according to the current specification is far greater than the monitoring values. Under the same geological and foundation pit depth conditions, the vertical prestressed anchor cable at the back of the new retaining wall structure can effectively increase the stiffness of the retaining wall, exhibiting good deformation resistance and engineering cost performance; The stress analysis method, calculation model and calculation formula of algorithms 1 and 2 can better simulate the actual mechanical deformation of the new retaining wall structure, and provide theoretical support for the application of the new retaining wall in practical engineering.