In response to the lack of domestic open-source role-customization system plug-ins in the field of computer game development, a Unity3D-based role-customization system plug-in, Ark Avatar Customization (AAC), is designed and implemented. AAC supports to change game characters’ dress-up and adjust their bone parameters, appearances and colors in a visual way, enabling role-customization required by developers and players. This study takes Unity3D as a platform for software development to fulfill customization functions and optimize system performance with the improved texture merge algorithm, editor extension, and prefab optimization. Performance comparison reveals the time and space cost of AAC are lower than that of existing techniques, proving the practicability of the designed role-customization system plug-in.