We have investigated the electronic structure of p-type ZnO by adopting the ab-initio study of plane wave ultra-soft pseudo potential technique based on the density function theory (DFT). The cell parameters, total density of states (TDOS) and partial density of states (PDOS) of N atoms were obtained after optimizing the structure of ZnO. It was shown that the volume of the primitive cell decreases with increasing content of the dopant. The p-type conductivity was realized easily by codoping with N and Al in the ratio of 2∶1, compared with doping with N alone. As the doping proportion increases, the carrier concentration was increased and the mobility was enhanced, which leads to the improvement of the conductivity.