Aiming at the difficulty in cold forging of optical module housings due to their complex structures, a finite element model was adopted to conduct an in-depth study on the non-uniform die cavity filling and the formation mechanism of metal folding during the cold forging process, and a partition-controlled blank optimization method was proposed as a solution. Firstly, the overall and cross-sectional characteristics of the optical module housing were analyzed. Based on the product features, a single-pass die forging process was developed, the die parting surface, draft angle and flash groove were designed, and the size of the uniform-thickness blank was preliminarily determined. Then, a finite element model was established to analyze the non-uniform filling law of the die cavity during the cold forging of the optical module housing from multiple perspectives, including the overall filling of the die cavity, flash formation, metal flow velocities in the X and Y directions, and comparative filling of characteristic cross-sections. Furthermore, the material flow velocity nephograms and grid diagrams of four rib-web characteristic cross-sections were extracted to reveal the formation mechanism of cold forging folding in the optical module housing. The results show that a smaller web thickness and a lower rib aspect ratio lead to a greater difference in metal flow velocity and more severe metal backflow, eventually resulting in a higher tendency of folding defects. Finally, a partitioned blank optimization design method was proposed to precisely control the regional volume distribution and blank profile, promote rib filling, improve flow uniformity, and prevent folding. Simulation and experimental verification demonstrate that the optimized scheme significantly enhances the forming fluidity, effectively eliminates folding defects, obviously reduces the forging pressure, and greatly improves material utilization. This study can provide a reference for the cold forging process of optical module housings and complex ribbed plate components.