Conformal cooling molds manufactured via laser selective melting (SLM) technology can significantly improve processing efficiency and effectively reduce production costs because of their excellent cooling performance, making it an important development direction for future injection molding molds. However, there are still many challenges in using SLM technology to form circular flow channels inside conformal cooling molds. During SLM, the structure of the circular flow channel inside the conformal cooling mold mainly presents as an overhanging circular hole structure. Defects such as warping and powder sticking are likely to occur if the overhanging circular hole structure is formed directly via the traditional processing strategy. Moreover, owing to the complex characteristics of the internal flow channel, it cannot be formed by adding support assistance. By adding a support structure on the outside of the mold, the forming angle of the mold can be adjusted to enhance the self-supporting ability of the overhanging circular hole structure, but this increases the additional forming time and material, resulting in increased production costs. Optimizing the non-supporting forming  process of the overhanging circular hole structure to meet the quality requirements of the conformal cooling mold for runner forming without adding support structures can effectively reduce the production cost of the conformal cooling mold and obtain high-quality molded parts. In this study, the forming process strategy for metal overhanging circular hole structures was optimized. Taking the 316L stainless steel overhanging circular hole structure as the object, the influences of the process strategy and hole diameter on the forming quality of overhanging circular holes were analysed. A bottom surface process area division strategy based on the adaptive angle of the processing layer was adopted to study its applicability for the formation of unsupported metal overhanging circular holes. The process was then used to manufacture a cooling mold sample, and the forming quality of the finished part was analysed. The results show that the adaptive lower surface process area division strategy based on the processing layer angle significantly suppresses the warping behavior during the forming process. The conformal water-cooled mold sample formed via the optimized process strategy has no significant quality defects, and the surface quality and forming accuracy of the internal flow channel meet the requirements for use.