Using MATLAB software to deal with ball images which come from the ball making experiments of a biological electron laboratory, to get its size parameters for the follow-up hemoglobin analysis experiment, involving image enhancement, image morphology, watershed algorithm and so on. Aimed at the conglutination phenomenon between small spheres, designing an improved watershed algorithm, that is, first of all, distance transforming the binary image, and then reconstructing the distance transform map by using morphological opening reconfiguration operation, so the weeny wave was avoided and intrinsic configuration remained. Finally, separating the reconstruction plan by using standard watershed algorithm. Experimental results show that this method can prevent excessive segmentation effectively.