Abstract: To preserve topographic feature during simplifying of contour line groups, a progressive simplification method is proposed. Firstly, topographic feature points and lines are extracted from contour lines according to expert rules. Secondly, both the extracted topographic feature points and lines as constraints are quantified as control variables. Based on the progressive graphics simplification approach, the non-feature points, feature points, feature lines and its associated bends on the contour lines are selected or deleted progressively according to the value of control variables so as to realize simplification of contour line groups with intelligence. Experimental results show that the proposed methods can effectively preserve topographic structural feature and improve the intelligence during contour line simplification.