Outdoors the living waste water after using A/O removes phosphorus was taken as matrix to start the biofilter of CANON process, aimed at the problem that nitrite oxidizing bacteria (NOB) excesses proliferation in CANON process and causes the effluent nitrogen concentration to exceed the first level A discharge standard of pollutants for municipal wastewater treatment plant, to experiment and investigate the effect of high ammonia loading rate, back washing and anaerobic operation on the NOB in the filter column. The results show that the NOB had adaptability to the high ammonia loading rate, when the influent ammonia nitrogen loading rate was 0.60kg/(m³·d), after the continuous operation of 80d, the total nitrogen removal rate was stable at 65% or so, the maximum effluent total nitrogen concentration was 15.8mg/L, exceeding the first level A emission standards; NOB was eluted in CANON process by the means of reverse washing, after the back washing the total nitrogen concentration of the continuous 40d effluent was less than 10.5mg/L; the inhibitory effect of anaerobic operation on NOB was larger but its inhibitory effect on AOB was smaller, from after anaerobic operation recovers low DO stable operation, the total nitrogen removal rate above continuous 40d was greater than 80%, and the maximum effluent total nitrogen concentration was 9.5mg/L.