Abstract: In this study,0.1,0.5 and 2.0 μg/mL of ciprofloxacin were used as experimental drugs to study the stress response of Lactobacillus plantarum derived from gut under active stress of ciprofloxacin,so as to provide theoretical basis for the development of probiotics with the ability to resist antibiotic stress and maintain the microecological balance of intestinal flora. Results showed that,the overall viability of the cells showed a downward trend,and the cell viability decreased with the increase of the concentration of ciprofloxacin. By observing the cell membrane integrity of the cells,it was found that the damage of cell membrane integrity was positively correlated with the concentration of ciprofloxacin. The lateral diffusion rate of the cells was measured to reflect the cell membrane fluidity,the results showed that 2.0 μg/mL of ciprofloxacin significantly reduced the cell membrane fluidity of the cells,which was reduced by 39.93% compared with the control group(P<0.01). Observation of the ultrastructure of the cells revealed that ciprofloxacin significantly changed the cell morphology of Lactobacillus plantarum,which could cause cytoplasm leakage and even cell death in severe cases. The results of the activity of key enzymes in cell glucose metabolism showed that the activities of hexokinase,pyruvate kinase and lactate dehydrogenase significantly decreased after treatment with 2.0 μg/mL ciprofloxacin(P<0.01),and after 0.5 μg/mL ciprofloxacin stress,the lactate dehydrogenase activity increased compared with the control lactate dehydrogenase activity(0.069±0.002) U/mg prot,and the enzyme activity was(0.081±0.006) U/mg prot(P<0.01). After further repeatedly stress on the cells with ciprofloxacin at a concentration of 0.5 μg/mL,the activity of lactate dehydrogenase was determined to be(0.126±0.004) U/mg prot(P<0.01). It indicated that under the stress of low concentration of ciprofloxacin,Lactobacillus plantarum produced stress response,initiated self-protection mechanism and resisted antibiotic adverse stress,which provided important technical support for the development of intestinal probiotic preparations.