The present study has successfully applied fuzzy control logic in controlling the weld line position for an injection-molded part. Although only a simple molded part was dealt with here, the incorporation of fuzzy control with CAE software in controlling the weld line position is a breakthrough in the concept of mold-design optimization. During the analysis, only four calculations of decision and simulation were conducted before the final result was obtained, saving considerable time compared with conventional trial and error or computer simulation methods. Consequently, the mold-design process can be accelerated. Since the weld line does appear at the expected location in the actual molded part, the present results can provide a sound basis for developing mold-design optimization. Future works under consideration include: 1)Apply the present approach to molded parts with complex geometry.2)Apply the present approach to molded parts with two or more gates, i.e., two or more output variables are necessary, as IF E is MP and V is NP, THEN U1 is SP and U2 is NP 3)Membership functions and some rules are established by neural networks so as to reduce manual input.