Based on a detailed discussion on the energy function representation of the structure extraction problem and through proper transformaton and arrangment of the energy function representation, the present paper has introduced beher order associated nonlinear continuous time neural net to the extraction problem of characteristic structure.This method is directly perceivable and understandable. It makes the characteristic structure to be extracted directly correspond to the output when the net is stable. and can conduct self-adaptive tracking and evaluation, thus opening up a new field in the extraction of charatrtidtic structure.