Quantum Hall effect (QHE), a quantized version of Hall effect, was observed in two-dimensional electron systems more than 30 years ago [1-3], in which the Hall resistance is quantized into h/e2 plateaus (h is Planck's constant, e the electron's charge, and is an integer  or a certain fraction ). Occurrence of QHE relies on the formation of well-defined Landau levels, thus is only possible in high mobility samples and strong external magnetic fields. In this talk, I report the experimental realization of quantum anomalous Hall effect (QAHE) , a quantized version of anomalous Hall effect, in thin films of Cr-doped (Bi,Sb)2Te3 magnetic topological insulator [5, 6] grown by molecular beam epitaxy. At zero magnetic field, the gate-tuned anomalous Hall resistance exhibits a quantized value of h/e2 accompanied by a significant drop of the longitudinal resistance. The longitudinal resistance vanishes under a strong magnetic field whereas the Hall resistance remains at the quantized value. I will also discuss about possible opportunities in Majorana fermions detection and less-power-consumption electronics based on QAHE. References: 1. K. v. Klitzing, G. Dorda, and M. Peper, Phys. Rev. Lett. 45, 494 (1980). 2. D. C. Tsui, H. L. Stormer, and A. C. Gossard, Phys. Rev. Lett. 48, 1559 (1982). 3. R. B. Laughlin, Phys. Rev. B 23, 5632 (1981). 4. C. Z. Chang et al., Science 340, 167 (2013) 5. M. Z. Hasan and C. L. Kane, Rev. Mod. Phys. 82, 3045 (2010). 6. X. L. Qi and S. C. Zhang, Rev. Mod. Phys. 83, 1057 (2011).