Edge detection is realized by using a FitzHugh Nagumo model which is one type of partial differential equations. This model has three types of dynamic, excitable, Turing/Hopf bifurcation, and bistable. In the excitable region the model can realize the edge detection. In the simulation only one image is processed in order to confirm the effect of control parameters on the edge detection. A satisfying effect of edge detection can be obtained by choosing appropriate control parameters. By comparing with other operators it is found that the FitzHugh Nagumo model is superior to Canny operator, Prewitt operator, Roberts operator, and Sobel operator on edge detection.