Abstract: This paper presents the design method, implementation technique, and the main functional property of the "Large-Scale Engineering Topographic Map Drawing System". This System constructs a practical cubic spline to sol ve the problem of crossing contours, which often occur while smoothing procedure is adopted in areas of very close contours.We also propose a 2 \frac12D hiddenline algorithm to remove the intersection among symbols of surface feature, elevation numbers and contour lines. This system can process the topographic maps of arbitrary boundary and all kinds of scale.