Abstract: Combining the API object's characteristics and the relevant circumstances of the tap, Software SolidWorks is used to realize the secondary development of three-dimensional parameterized design of taps in Delphi programming environment. The specific processes and key technologies are introduced. The approach presented solves the complex parametric modeling problems involved in the design and calculation of tap parameters, and improves the design efficiency, provides a shortcut for the design and development of taps as well.