Insulator location is a premise condition of noncontact creepage distance measurement. Dependent on the morphology and distribution characteristics of the insulator, we proposed a method of insulator localization based on Hough transformation and RANSAC algorithm. Firstly, we obtained the edge of the insulator image with Canny edge detection, and dependent on the characteristics of the insulator is shaped like a circle, we combined Houghcircle transformation to test. Secondly, according to the characteristics of the insulator spacing roughly equal and the insulator string like a straight line, we fitted the center points of the circles with the modified RANSAC algorithm. Finally, we traversed the straight line and located insulator with a red rectangular box. The experimental results have shown that this method can locate the insulator effectively, which provides the basis for the subsequent research of the insulator detection and so on.