This paper studied the economic design of the unilateral template and support system for the current use in underground engineering cast-in-place concrete external wall and unilateral template system as the internal model of exterior wall construction. The corresponding force mechanic model was established through the analysis of the working conditions and stress state of the cast-in-place single-side concrete formwork templates and the support system. Furthermore, an economical ultimate state design method was proposed to make full use of the material performance under the condition of meeting the functional requirements. The economic arrangement distances of the base and the secondary beam and support system as well as anchor bolt diameter were analyzed. The effect of saving material and reducing the construction cost were obtained after practical engineering computing applications.