Aiming at the problem of detecting the centers of touching particles images, a detecting method based on the improved Generalized Hough transform is proposed in this paper. The method firstly figures out the ring that overlaps the known particle's outline, then the overlapping area of the ring template is accumulated along the foreground contour of the image to be detected. Finally, the region maximum value of the accumulated matrix will be the centers of the particles. The ring template has rotation invariance so that the detection time will be shortened greatly. Meanwhile, the result shows that the method in this paper has fine detection effect.