We demonstrate a high-performance enhancement-mode ZnO TFT on a glass substrate. The ZnO thin film is deposited by RF magnetron sputtering with the presence of O2 at low temperature and optimized oxygen passivation conditions on the ZnO surface. When biased at the saturation region VDS = 10~20V and VGS = 5V, the IDS is as high as 0.85mA. The Ion/Ioff ratio is 1.47×106 and field effect mobility as high as 391.6 cm2/Vs. We believe the results are among the best ZnO TFTs ever obtained.