Abstract: Based on Moldflow, the melt fill mold processes of injection molding a door inside-decoration panel were simulated in this paper.By comprehensive analysis and comparison among some targets, such as fill time, injection pressure, clamp force, weldline strength, warpage and material utilization ratio etc., a design scheme of the runner system used in injection molding was optimized.The actual production showed that while injection molding the panel by making use of the running system designed optimally, the melt fill mold process and result corresponded with that of Moldflow analysis and prediction, and the panel quality met molding technical requirements.