The polar ZnO surfaces have received wide interests due to their higher activity than the non-polar facets in catalysis, photo-catalysis and gas sensitivity. However, the theoretical study on the relative stability of the polar ZnO surfaces is still limited. In this work, Am calculate the surface energy of the polar ZnO(0001)-Zn and Zn( ̅)-O surfaces. The Density-Functional Theory (DFT) method shows that the ZnO( ̅)- O terminal is more stable than the ZnO(0001)-Zn terminal because the polarizability of surface O-2 is higher than that of surface Zn+2, which is in good agreement with the experimental results. The density of states shows the three surfaces of ZnO-O are better than that of the surface in bulk; this is what makes them qualified in the field of catalysis.