Abstract:In this paper, the spring is taken as the research object. According to the principle of secondary development based on NX Open API, the basic functions of setting up secondary development environment, designing secondary development form and debugging secondary development program are discussed. On this basis, fast design method of three-dimensional spring is proposed, and the key technologies in the process of development and implementation are also discussed in detail, such as program structure, interface, and logic flow chart. The design results meet the requirements of theoretical calculation, it can provides support for secondary development based on NX.