In order to get more knowledge about the difficulty of conductivity-type inversion in ZnO, this paper performs the thermodynamical analysis of intrinsic point defects. Relations between the main defect concentrations and the environment pa rameters, such as the temperature and oxygen pressure, have been formulated unde r thermodynamical equilibrium. The K-V figure is presented. It is shown that it is very difficult to obtain p-type conductivity under thermodynamical equili brium. Based on these facts, this paper gives the effective approaches to realize p-type conductivity inversion. The feasibility of the analysis is also pro ved by some experiments.