Considering the professional features of steel connection-joint design, this paper developed a new computer-aided design (CAD) program which is aiming at solving problems that the connection-joint design results unsuitable for human intervention of the software developed by our country. Program developing and researching is adopted the object-oriented development technique C++ to provide a flexible interactive function which can not only achieve the whole building's automatic connection-joint design of three-dimensional framework but also nodes merging, node design results modification and re-checking by designer. The program can make the connection-joint design of framework fast, simple and accurate to improve engineering efficiency. The achievement has been used in each module of the PKPM series steel structure design software as base class library of steel connection design in dynamic library plug-in form and obtained good application effects.