The recognition of scanned image of engineering drawings and the extraction of character strokes are very difficult in pattern recognition. To overcome the shortcoming of thinning algorithm, many global algorithms are devised. Among them the global algorithm based on graphical segment directly recognizes the image through the macro-features of image. But it can’t process curve and character image. The new algorithm takes scan strip as the basic image process unit and scans the whole image dynamically. A parameter head having been set up is used to supervise the succeeding trace procedure, so more precise vectorization result is obtained. The satisfying result of processing many different kinds of image, including Chinese character image, indicates that the new algorithm is powerful and adaptive.