The anaerobic ammonium oxidation was successfully started up within 144 d in attached microbial film expanded bed reactor with bamboo carbon as carriers. The maximum nitrogen removal rate reached 3.02 kgN/m3/d, which was the highest level in China. The reactor has a great potential in nitrogen removal compared to the theoretical value 12.77 kgN/m3/d deduced from dynamic fit. As the start-up course experienced autolysis phase, activity lag phase and activity elevation phase, the seed sludge turned from khaki flocs to sandy brown granules and finally to red granules. These red granules with a relatively high anaerobic ammonium oxidation(ANAMMOX) activity of 0.56 mgTN/(mg protein)/h were major contributors to the ANAMMOX process in the reactor.