Abstract:［Objective］ The purpose of this work was to screen strains having tobacco-specific nitrosamines (TSNA) deteriorating activity，isolated from the inner and superficial of tobacco plants． Then strain AS97 was isolated and identified for further application.[Methods] Strain AS97，with the highest conversion ability against both nitrate and nitrite，was screened by enrichment and selective medium． The strain was identified by rphological，physio-biochemical characteristics and 16S rRNA gene sequence analysis．The concentration of 4-(methylnitrosamino)-1-(3-pyridy)-1-butanone (NNK)，N-nitrosonicotine (NNN)，N-nitrosoanatabine (NAT) and N-nitrosoanabasine (NAB) were determined by LC-MS/MS．The fermentation broth of strain AS97 was spraied on the leaves of tobacco to define inoculum concentration and fermentation condition. [Results] AS97 was identified as Pseudomonas fluorescens (Genbank accessionnumber:JF 449445)．Under the optimal growth conditions with inoculum concentration of 5%，at 30℃ for 10 d，AS97 had high biological activity against NNK and NNN with a degradation rate of 59. 08% and 38.79%，respectively．The correlation analysis displayed a pronounced correlation(p ＞0.01) among the concentration of nitrate，nitrite and TSNA．Furthermore，the results also exhibited that nitrate and nitrite were antecedent substance of TSNA. [Conclusion] These results indicated that Pseudomonas fluorescens AS97 could be a promising microorganism in the practice of non-harmful cigarette production．