The manual computer interaction aeromagnetic tangent method system is designed according to the flowchart of the manual tangent method. It combines manual experience and wisdom with strong computer power in calculating, consulting tables and processing graphs. It has many useful functions. Single profiles or multiple profiles can be displayed, zoomed and moved; characteristic lines and points can be protracted automatically and amended by manual computer interaction; depth, width and magnetization of magnetic body can be calculated automatically; results can be saved and displayed; visualization and work efficiency are improved considerably. Therefore, a great deal of work can be reduced. It also provides different means for effective interpretation of aeromagnetic anomaly. This system is developed with the VC + + development tool and is object-oriented. It can be applied on the win32 system.