Changes of sensory,chemical and microbiological properties,as well as bacterial flora in cultured tilapia(Oreochromis niloticus)during chilled storage at 0℃,5℃ and 10℃ were investigated.Total viable count(TVC),the count of Pseudononads spp.and total volatile basic nitrogen (TVB-N)in newly-caught tilapia were determined to be(4.79 ± 0.60)lg cfu/g,(4.00 ± 0.75)lg cfu/g,and(8.08 ± 0.29)mg/100 g,respectively.The complex bacterial flora consisted of 80.5％ gram negative bacteria and 13.6％ gram positive bacteria,and was dominated by Pseudomonas spp.(36.5％),Aeromonas spp.(15.3％)and Enterobacteriaceae(14.2％).At the end of the shelf life of storage under 0(20 days),5(9.5 days),and 10℃(5 days),fish freshness showed similar changes with the values of TVC,the count of Pseudomonas spp.,and TVB-N all increased to(8.08 ±0.41)lg cfu/g,(7.70 ±0.11)lg cfu/g,and(20.1 ± 1.66)mg/100g,respectively.Growth dynamics model fitted by the modified Gompertz equation showed that the growth of Pseudomonas spp.was slow during the initial phase of chilled storage at 0℃,5℃ and 10℃,having the lag phase of(59.63 ±61.88)h,(7.25 ±24.06)h and(3.95 ±9.83)h,respectively.During the exponential growth phase,the specific growth rates at 0℃,5℃ and 10℃ were(0.02 ±0.00),(0.04 ±0.00)and(0.08 ±0.01)h-1,respectively.The maximum specific growth rate at the lowest temperature 0℃ was significantly lower than those at 5 and 10℃.During the chilled storage,the growth of both Enterobacteriaceae and Aeromonas spp.were inhibited,and the bacterial flora gradually became single.On the other hand,cold-adapted gram negative bacteria gradually increased,and their percentages at the end of shelf life during storage under 0℃,5℃ and 10℃ reached 86.4％,91.7％ and 95.7％,respectively.Among those,Pseudomonas spp.increased most significantly,consisting of 81.8％,69.4％ and 57.4％,respectively,of the total isolations at each of the temperature.According to the bacterial identification system,and based on the bacterial colony and cell morphology,physiological and biochemical characteristics,the major spoilage bacteria at the sensory acceptable borderline in tilapia during 0,5 and 10℃ storage were identified to be Pseudomonas spp.,mainly consisting of Pseudomonas fluorescens,Pseudomonas putida,Pseudomonas aeruginosa,and Pseudomonas alcaligenes.Pseudomonas fluorescens,the most dominant bacteria,contained 50.18％ monounsaturated fatty acid(MUFA)that was composed of 16 ∶ 1 ω7c,iso-15 ∶ 0,16 ∶ 0,and 17∶1ω8c,at the ratio of 26.16％,14.83％,7.96％,and 3.94％,meanwhile its ribo-type detected with Riboprinter was 56-S-7 with a similarity coefficient of 0.85.