Objective To investigate the prognostic value of serum chloride ion concentration in critically ill or clinically stable patients with decompensated cirrhosis. Methods A retrospective study was conducted among the patients with decompensated cirrhosis who attended the intensive care unit （ICU） and Department of Gastroenterology， The First Hospital of Lanzhou University， from January 2017 to January 2022，and the patients were divided into ICU cohort and Gastroenterology cohort. The outcome event for the ICU cohort was in-hospital death. A logistic regression analysis was used to investigate the association between serum chloride levels and ICU mortality rate； the receiver operating characteristic（ROC） curve was plotted and the area under the ROC curve（AUC） was calculated to assess the value of blood chloride level in predicting ICU mortality rate. The patients in the Gastroenterology cohort were followed up with the outcome event of all-cause mortality rate， and the Cox regression analysis and the Kaplan-Meier analysis were used to investigate the value of blood chloride level in predicting mortality rate. Results In the ICU cohort， serum chloride ion was significantly associated with in-hospital mortality in the ICU（odds ratio=0.934， 95%CI=0.871-0.993，P=0.035），and blood chlorine had an AUC of 0.687 in predicting in-hospital mortality in the ICU. In the Gastroenterology cohort， serum chloride ion concentration was significantly associated with mortality rate in the subgroup with a Child-Pugh score of <10 （hazard ratio=0.906，95%CI=0.822-0.997，P=0.043）， and hypochloremia was associated with a lower survival rate. Conclusion Hypochloremia is associated with the increase in mortality rate in patients with decompensated cirrhosis.