Abstract: The biological activity of a biotrickling filter determines the capability of a biological treatment plant in treating organic waste gas，and the most important factor affecting the bioactivity of activated sludge is the microbial community.In order to understand the microbial community structure，diversity and abundance in a biotrickling filter，metagenomic technology was used to analyze the microbial diversity of filler solids in the biofilter of volatile organic compound treatment system.The results show that the relative abundance of bacteria，eukaryotes，archaea，viruses in biotrickling filter are 89.34%，1.99%，1.06% and 0.03% respectively，and the microbes are assigned to 75 phylums，195 classes，395 orders，752 families and 1798 genera.Bacteria in activated sludge are mainly Proteobacteria，Actinobacteria，Bacteroidetes，Firmicutes and Chloroflexi.In addition，18 toluene degrading bacteria strains，21 xylene degrading bacteria strains and 15 butyl acetate degrading bacteria strains were screened from the activated sludge using the only carbon source medium，which were mainly identified as Acinetobacter sp.and Pseudomonas sp..The degradation rates of 100 mg/L toluene，p-xylene and m-xylene are 99.98%，99.89% and 88.34% within 48h by the degrading strain CX20.The butyl acetate degrading strain CBA12 can completely degrade 100mg/L of butyl acetate within 48h.The isolated strains show good VOC degradation ability and have a wide application prospect in the field of waste gas treatment.

Key words: biotrickling filter, activated sludge, microbial diversity, metagenomic technology, microbiota, VOC degrading bacteria