A discussion is given about the focusing of optical beams due to the cross-phase modulation in three-dimensional self-defocusing nonlinear media. The effect on the focusing of the probe beams for the three initial parameters is discussed: the amplitude of the pump beam, the separation between the pump and the probe beam centers and the wavelength ratio of the pump and the probe beams. The coupled amplitude equations are optimized based on the fact that the probe beam is much less intense than the pump beam, and cut the time of operating the programs much too. Our numerical results show that, the greater the amplitude of the pump beam and the wavelength ratio of the pump to signal beam are the better the probe focuses; the initial separation between the pump and the probe beams has an optimum values. The results can be used to design experiments in order to obtain the best effect of the focusing.