Abstract: Overlapping separation of tracks is the core issue of particle tracks measurement. Aiming at the ultra-dense particle track microscopic image with features such as high density of particles, severe overlap of tracks, different level of granularity, uneven internal gray scale of tracks, and impurities existence, etc., the problems of the existing overlapping separation algorithms were analyzed, and a new method was proposed. The first step was enhancement for track microscopic image. Then the extended max segmentation was taken, and overlapping tracks were separated by mathematical morphology and area ratio method. At last, special process for tracks at the edge and single tracks with no hole was adopted. Experimental results show that the algorithm can process the track microscopic image effectively, locate the contours of tracks quickly and accurately, and separate dense overlapping particle tracks.