RESULTS: Severe asthmatics had lower FEV1% predicted (57.2% vs. 86.4%, p<0.001), higher sputum eosinophil (19.5% vs. 9.0%, p<0.001) and longer duration of asthma[10.0 years vs. 7.5years, p<0.05] compared to non-severe asthmatics. There was no statistically difference in OTU numbers and diversity score between severe asthmatics, non-asthmatic and healthy subjects. At the phylum level, the difference of OTU relative abundance remained non-significant. But at family level, severe asthmatics had significant more abundance of Pseudomonadaceae (1.50%vs.0.05%, p<0.001) and Enterobacteriaceae (1.35% vs.0.01%, p<0.05) compared to non-severe asthmatics. Eosinophilic asthmatics also had more abundance of actinomycetaceae (1.35% vs.0.51%, p<0.05) compared to non-eosinophilic asthmatics. The abundance of actinomycetaceae at family level is very closely related to sputum eosinophils in asthmatics (r=0.36, p<0.01). Meanwhile, the abundance of bacteroidaceae is positive correlated with FEV1%pred (r=0.335, p<0.01).