Morphology is used for edge extraction of binary image.In particular,Discrete-time Cellular Neural Network(DT-CNN) is introduced into binary morphology owing to the natural corresponding relationship between them,and then the morphology operation is transformed into multi-layer DT-CNN under some specific template.Multi-layer DT-CNN is transformed into Monolayer DT-CNN by optimizing design to reduce the complexity of the operation.Therefore,we can extract the edge of gray image by synthesizing the edge detection result of each bit in the pixel.Compared with the traditional Sobel and Log operator,the method has a better performance and converges quickly.