Abstract: This study aims to address the core bottleneck hindering the implementation of intelligent manufacturing in the field of complex equipment manufacturing—namely, the lack of lean design and standardization in production processes. To this end, a lean-based production process design method is proposed and investigated, focusing on three key transformation processes from product process to production process: the refinement of processes into elemental operations, the reorganization of processes into workstations, and the in-depth optimization of production processes. Through case studies of the packaging operation at Company A and the assembly line for optical equipment at Company B, methods such as work measurement, standard work combination charts, and improved process flow diagrams are applied to systematically validate the effectiveness of the proposed approach. The results demonstrate that this method significantly enhances production efficiency and process standardization: without additional automated equipment, the required labor for the packaging operation is reduced by 19%, the per-capita efficiency of the assembly line is increased by 420%, and a manufacturing bill of materials along with a refined process flow model that directly supports intelligent manufacturing operation are generated. The lean production process design framework established in this study provides an operable methodological basis for the systematic implementation of intelligent manufacturing, highlighting the critical path of achieving high efficiency, digitalization, and intelligence in manufacturing systems through front-end lean process design.