To contract the circular beam symmetrically, the co-propagation of the bright and dark beams in three-dimensional self-defocusing media is studied systematically. Numrical results indicate that the signal beam is induced to the focus and symmetrically contracted during the evolution due to the cross-phase modulation effect by the pump beam, when the two beam centers are completely superposed and the initial intensity of the dark pump beam is much stronger than that of the bright signal beam. The effect of the beam parameters on the focusing performance of the signal beam is discussed, and it is found that the larger the initial intensity of the pump beam is, the stronger the focusing of the signal beam is. There exists an optimum value for the initial spot size of the dark beam for the strongest focusing of the signal beam, for a given initial pump intensity. When the wavelength ratio of the pump beam and the signal beam is 0.5～1.5, the focusing of the signal beam decreases with the rise of the ratio. And the theoretical result is validated experimentally.