Abstract: Based on the pretreatment for smooth denoising and contrast enhancement of the speckle fringe patterns, the central skeleton lines of the interference fringes were obtained with the method of edgeextracting, filling and thinning for the electronic speckle fringes. The deficiency in extraction for the skeleton lines of the interference fringes, which can not be overcome by some common algorithms such as binaryzation and thinning due to the strong-noise characteristic of the electronic speckle interference fringes, was overcome by this method. The result shows that the method can find the skeleton lines precisely and provide a new method for achieving the line of equal displacement in the plane displacement field.