Nowadays, most designs of tunnel excavation are manual, and the designs have a poor quality and slow speed. To solve these problems, the component and structure of blasting design system of tunnel excavation based on CAD technology are studied. On the basis of comprehensive analysis and influence factors, a basting CAD auxiliary system based on ActiveX interface and VBA interface technology is developed for blasting design about tunnel excavation. Some function modules, including system management, arrangement design of hole, construction design, parameter calculation, blasting data and construction information management, can meet the demands of system function. A design of blasting example of tunnel excavation shows that the system can carry out blasting design with high speed accurately. The design can also avoid the dependence of personal experience. Meanwhile, the work of blasting design becomes more reasonable. Design results can be reliable and practical. Further, the system has some advantages, such as high speed and excellent transplantation. The system has positive significance for economic benefit of coal production.