Using the density-functional theory, the electronic structures of pure and Li-N, Li-2N codoped wurtzite ZnO systems are explored. It is find that Li-N and Li-2N codoped wurtzite ZnO systems each cause the Fermi level to cross the top of the valence band and to form shallow acceptor level, which indicates that p-type ZnO system can be obtained by codoping Li and N. Moreover, the carrier concentration is enhanced in the Li-2N codoped system and this structure is more favorable for the formation of p-type ZnO.