P-type conduction is a great challenge for the full utilization of ZnO due to low dopant solubility and high acceptor ionization energy. We investigate formation energies and transition levels of the defect complex m AlZn-nNO in ZnO by the first principles. The formation and ionization energies for isolated mNO in ZnO are 1.17eV and 0.439eV, respectively. Among all complexes investigated here, formation and ionization energies of the complex AlZn-2NO can be reduced to 0.632eV and 0.292eV, respectively, which indicates that the defect complex is a relative better candidate for p-type ZnO. However, the results calculated from density of states show that 4AlZn-NO doped ZnO takes on n-type conduction.