Abstract: The algorithm of image segmentation and parameters calculation for over-lapping nuclear track image is studied. The method of the Otsu global threshold and distance transformation was proposed, the distant image was converted to a binary image, and the overlapping nuclear track was effectively segmented. The parameters calculation of the nuclear track, such as area, perimeter, roundness, centroid, was completed based on these methods. Computer simulation results show that the algorithm is concise, efficient and processed automatically.