Computer aided borehole design and trajectory monitoring are necessary conditions for the information and digital development of drilling engineering. Thus, the further research on the application of computer aided design technology is important for drilling engineering in theory, technology and methods. The drilling design and trajectory dynamic monitoring system is mainly based on the design of drilling trajectory control parameters in directional drilling engineering and drilling trajectory analysis monitoring, including drawing of 2D graphics and 3D graphics of drilling trajectory and module functions of drilling engineering technical documents automatically generating, such as comprehensive charts, drilling geological design documents and drilling geological histograms, and so on. Drilling design and trajectory monitoring can be automatically made by powerful functions of computer in data processing and computing, graphics drawing and generation and by software programming and data entry. This system software is not only suitable for directional drilling engineering design and process monitoring, but also can be used as a component part of electronic files and digital management system of drilling engineering. This software system has been tested in the engineering practice, the desired application effects are achieved.