In this paper, a new interactive algorithm for image segmentation is proposed. First, threshold segmentation is applied to the original image, and the corresponding foreground image and background image are obtained. In the foreground image, some manually selected contour pixel points of the pattern to be segmented will become the initial seed points. The set composed of seed points is defined as set E. Then, the distances between each pixel point in foreground image and each seed point in set E are computed. If the minimum distance is less than the threshold, the pixel point with minimum distance is labeled as seed point, and added to the set E. Until all the pixel points in the foreground image have been labeled, the seed points in the final set E compose the segmentation image. At last, the effectiveness of the proposed algorithm is proved by a simulation.