In this paper an improvedmethod of image segmentation based on threading detection is present. Themeth-od is used to segment the image of dial of the electricmeasuring instrument. Themethodmakes use of the geometrical characteristic of the object. The line ( row) of image is segmented by a threshold value, and the length of the biggest subsection is calculated. The segmentation points are found through analyzing the change of the biggest subsection.Thismethod overcomes the shortcoming that the demand to the quality of image is too strict. The experimental result shows that the effect of the method is very good.