Abstract: Hyperboloidal-type normal circular-arc gear is a new development of circular-arc tooth profile in the gear pair with crossed axis. In this study, a parametric modeling method for hyperboloidal-type normal circular-arc gear is developed. A series of mathematical representation for this gear are presented and a surface element, including the datum surface and the tooth surface, is utilized as the basic unit of gear modeling and the surface boundaries are solved by golden section search method. According to the generation theories of surfaces, the surface element is discretized to produce the data for generating the gear model. By using the programming tool VC++ 6.0 and Open Graphics Library (OpenGL), a 3D parametric modeling software package for this gear is developed. The results laying foundation for computer aided design and analysis of hyperboloidal-type normal circular-arc gear.