Abstract: A simple data reduction is first applied to the digitized curve.Chromosomes are defined by encoding the point sequence into binary strings to represent the digitized curve. Each bit of binary strings is called a gene.Each polygonal approximation is mapped to a unique binary string.The objection function is defined as the mean square errors between the given digitized curve and the approximated polygonal. Three genetic operators‚namely selection‚crossover and mutation‚are constructed to solve the problem.Points of 3D digitized curve corresponding to genes of a chromosome‚equal to1s‚ are demarcation ones.Experimental results show that this approach can get more accurate result of approximation.