The electronic structures and magnetic properties of pure ZnO and doped Zn36-nMnO36, in which M represents the transition metal Mn, Fe and Co (n = 1, 2 and 3 atom) were calculated by using the ab initio methods within the density-functional theory (DFT) . The DFT was based on local density approximation (LDA) of exchange correlation potential. The results showed that the Zn36O36 has the minimum total energy. The energy gap of Zn36O36 calculated by LDA was 1.2 eV which was underestimated due to the method being used. In the case of doped Zn36-nMnO36, there were the energy levels of electrons appearing in the energy gap. The calculated magnetization of Zn36O36 revealed that the pure ZnO is nonmagnetic while the doped Zn36-nMnO36 are ferromagnetic. Among the doped spiecies, Zn33Mn3O36 has the highest of magnetization, which 14.70808 .