We experimentally find that the ZnO thin films deposited by dc-magnetron sputtering have different conduction types after annealing at high temperature in different ambient.Hall measurements show that ZnO films annealed at 1100℃ in N2 and in O2 ambient become n-type and p-type,respectively.This is due to the generation of different intrinsic defects by annealing in different ambient.X-ray photoelectron spectroscopy and photoluminescence measurements indicate that zinc interstitial becomes a main defects after annealing at 1100℃ in N2ambient,and these defects play an important role for n-type conductivity of ZnO.While the ZnO films annealed at 1100℃ in O2 ambient,the oxygen antisite contributes ZnO fihns to p-type.