Included angle chain is a coding method to describe curves with included angle which is produced by a string of directional and equal line segments.Included angle chain of chang eable length is put forward.For a given curve,it can be described by finite directional line segments and include angles within permissible error,and the line segments are not equal,each included angle is betw een two joined line segments.These ang les and length of line segments const itute included angle chain of changeable length.In our chain code,the merit of included angle chain is kept down.Compared with included angle chain,in the case of using equal storag e space,our method may produce bet ter precision as describing a curve which hold more and dense inf lexions or hold more curvature variety.The proposed approach can be used in figure storage,rebuilding and matching.