Objective To explore the impact of gut microbiota imbalance on the prognosis of decompensated liver cirrhosis.Methods A total of 100 patients with decompensated liver cirrhosis in the Third People's Hospital of Zhengzhou from June 2021 to June 2024 were selected as the study group.Routine treatment was given to all patients upon admission,and the abundances of gut microbiota(Bifidobacterium,Lactobacillus,Escherichia coli,Enterococcus) were measured before treatment.Additionally,100 patients with liver cirrhosis compensation and 100 healthy individuals who underwent physical examinations during the same period were included as control group 1 and control group 2,respectively.The gut microbiota of the three groups was compared.After 6 months of follow-up,patients were divided into the good prognosis group and poor prognosis group based on their survival status.Baseline data and gut microbiota counts were compared between the two groups,and Cox regression analysis was used to determine the relationship between gut microbiota and the prognosis of decompensated liver cirrhosis.The receiver operating characteristic(ROC) curve was drawn,analyzing the value of gut microbiota imbalance in predicting the prognosis of decompensated liver cirrhosis.Results The abundances of Bifidobacterium and Lactobacillus in the study group were significantly lower than the control group 1,and those in the control group 1 were significantly lower than the control group 2.The abundances of Escherichia coli and Enterococcus in the study group were significantly higher than the control group 1,and those in the control group 1 were significantly higher than the control group 2(P<0.05).During the 6-month follow-up period,14 out of 100 patients in the study group died,accounting for 14.00% (14/100).The Child-Pugh grading,model of end-stage liver disease(MELD) score,and proportion of combined malnutrition in the poor prognosis group were significantly different from those in the good prognosis group(P<0.05).The abundances of Bifidobacterium and Lactobacillus in the good prognosis group were significantly higher than the poor prognosis group,while the abundances of Escherichia coli and Enterococcus were significantly lower than the poor prognosis group(P<0.05).According to Cox regression analysis,Child-Pugh grading,MELD score,combined malnutrition,Bifidobacterium,Lactobacillus,Escherichia coli,and Enterococcus were significantly correlated with the prognosis of decompensated cirrhosis(P<0.05).ROC curveshowed that the area under the curve(AUC) of abundances of Bifidobacterium,Lactobacillus,Escherichia coli,and Enterococcus in predicting the prognosis of decompensated liver cirrhosis alone or in combination was all greater than 0.7,which had certain predictive value,and the combined predictive value was higher.Conclusion Patients with decompensated liver cirrhosis have a higher probability of experiencing gut microbiota imbalance,and gut microbiota imbalance can increase the risk of poor prognosis in patients with decompensated cirrhosis,and can predict patient prognosis to some extent.