Abstract: This paper reported a study on the design process of the hot-runner bicolor injection mold for the automobile valve body. Based on the characteristics of the bicolor mold and relevant products, two types of thermoplastics were selected as the basic materials, i.e. PP/40 %PS blend and TPO. To meet the requirement of appearance, the two-plate style hot-runner point gate was adopted to ensure the automatic separation of the product and molten material at the gate point during the opening process. A special side core-pulling mechanism was designed, which was driven by spring force. This makes the slider and the limit block move mutually without separating, thus making the slider movement more stable and accurate. The independent hydraulic core-pulling was used to solve the problem that there are some special holes formed on the product. The actual production confirmed that the mold structure was reasonable and the product performance was steady, which met the requirement of production.