The quantum effects on the proton-transfer reaction in the N2H7+ cluster has been studied using the classical ab initio Monte Carlo method and a one-dimensional model for the quantum wave packet dynamics on the ab initio MP2/6-31 + G* potential energy surface. The optimized stable structure has C-3v symmetry, in which the proton is bound to one NH3 molecule in such a way that the proton feels bistable potential. In contrast, we found that the proton was located at the center of two NH3 molecules with D-3d symmetry due to the quantum effects of the proton kinetics. ne quantum simulations indicate that the reason the experimental spectra predict N2H7+ to have a symmetric D-3d Structure, contrary to the ab initio results, is that the quantum effects of the proton motion is completely neglected in the previous theoretical calculations. The vibrational frequency for the N-H stretching mode which corresponds to the proton transfer is estimated to be 706.7 cm(-1) by including proton quantum effects in contrast with 2100.1 cm(-1) obtained by the conventional ab initio MO method for the C-3v structure.