To characterize the microbial community in anaerobic ammonia oxidation (ANAMMOX) biofilter and to apply this technology, techniques of scanning electron microscopy (SEM), denaturing gradient gel electrophoresis (DGGE), cloning and sequencing were utilized to study the community structures in two up-flow ANAMMOX biofilters, which were operated stably at low temperature (150-165 ℃). The results of SEM showed that the filamentous bacteria were just found within ceramic packing B1 biofilter. Spherical bacteria had more densely distribution in volcanic packing B2 biofilter than that in B1 biofilter. Bacterial DGGE results showed that there were some differences between B1 and B2 microbial species and the population similarity was 681％, and B2 reactor had higher bacteria richness. However, the type of anammox bacteria existence in two reactors was the same. The sequences of bacteria and ANAMMOX 16S rRNA identification revealed that Candidatus Kuenenia stuttgartiensis occurred in two ANAMMOX bioreactors. It was helpful to apply ANAMMOX technology at low temperature (150-165 ℃) through Candidatus Kuenenia stuttgartiensis enrichment, with the form of biofilter reactor filled with volcanic rocks.