Rutherford backscattering spectrum of protons in H+2，H+3 cluster ions have been measured in channeling directions and of silicon crys tal. It has been found that, under the same velocity of 650 keV/p, the backscattering probability for protons of H+2 cluster ions is great er than that of H+ projectile, and the backscattering probability for protons of H+3 is gr eater than that of H+2. The ratio of backscattering yields of channeling di rection to that of random direction is defined and the depth dependence of ratio distribution is calculated.