The N+N-2 exchange rate is calculated using a time-dependent quantum dynamics method on a newly determined ab initio potential energy surface (PES) for the ground (4)A" state. This ab initio PES shows a double barrier feature in the interaction region with the barrier height at 47.2 kcal/mol, and a shallow well between these two barriers, with the minimum at 43.7 kcal/mol. A quantum dynamics wave packet calculation has been carried out using the fitted PES to compute the cumulative reaction probability for the exchange reaction of N+N-2(J=0). The J-K shift method is then employed to obtain the rate constant for this reaction. The calculated rate constant is compared with experimental data and a recent quasiclassical calculation using a London-Eyring-Polanyi-Sato PES. Significant differences are found between the present and quasiclassical results. The present rate calculation is the first accurate three-dimensional quantal dynamics study for the N+N-2 reaction system and the ab initio PES reported here is the first such surface for N-3.