Abstract: Thinning-based recognition algorithms are widely used in the field of automatic processing of engineering drawings.However,the current thinning processes perform out of shape at the node,which result in relatively low recognition rate of the primitive graphic elements.The node patterns after thinning are deeply analyzed,and the reason producing node deformation is discussed.A node regulation strategy which can effectively revise the deformation of node created in the thinning procedure has been proposed.The algorithm proposed in this paper has been applied to solve the practical problem successfully.