Abstract: To segment the overlapping blood cells，an approach based on the characteristic that the blood cells are disk-shaped is proposed.A distance map and the edge of image can be obtained by morphological erosion，while the regional centers and centers of circle can be deserved with grayscale reconstruction algorithm.After all of these，the edge of the blood cells is searched based on the circular characteristics to find the separating points and separating line，then the overlapping blood cells are segmented into singles accurately.The experimental results show that the proposed approach is feasible and effective.