Potential energy surfaces for the N(S-4, D-2, P-2) + H-2 reactions have been calculated using the ab initio multireference configuration interaction method. Two-dimensional surfaces were constructed for collinear and perpendicular approaches of N + H-2 in order to understand the mechanisms of these reactions. The calculations predict that not only the lowest doublet surface but also the second lowest doublet surface contribute to the reaction dynamics of N(D-2) + H-2 and that these two surfaces intersect with the lowest quartet surface of N(S-4) + H-2 in the intermediate regions. The mechanism of the quenching process for N(P-2) + H-2 is also discussed.