As an important component of cold side bleed for pneumatic system of civil aircraft, the fan bleed inlet directly affects the performance of the engine bleed air system. In this paper, the design process of the fan inlet was summarized, and the steps of parametric design, three-dimensional fluid dynamics simulation evaluation and wind tunnel test were adopted to achieve a closed design loop. The design requirements and design case selection principles were sorted out, the theoretical calculation methods of the main design elements were determined, a set of parametric design programs were developed, and the design results were verified by simulation and experimental methods. It provides guidance and reference for subsequent aircraft design, which can improve design efficiency.