Objective To analyze the expression level of triggering receptor expressed on myeloid cells-1 （TREM-1） in serum and ascites of patients with cirrhotic ascites，and to investigate its correlation with clinical features and inflammatory markers and its role in the diagnosis of infection and prognostic evaluation. Methods A total of 110 patients with cirrhotic ascites who were hospitalized in The Fifth Hospital of Shijiazhuang from January 2019 to December 2020 were enrolled，and according to the presence or absence of intra-abdominal infection，they were divided into infection group with 72 patients and non-infection group with 38 patients. The patients with infection were further divided into improvement group with 38 patients and non-improvement group with 34 patients. Clinical data and laboratory markers were collected from all patients. Serum and ascites samples were collected，and ELISA was used to measure the level of TREM-1. The independent-samples t test was used for comparison of normally distributed continuous data between two groups； the Mann-Whitney U test was used for comparison of non-normally distributed continuous data between two groups，and the Kruskal-Wallis H test was used for comparison between multiple groups； the chi-square test was used for comparison of categorical data between two groups. A Spearman correlation analysis was used to investigate the correlation between indicators. A multivariate Logistic regression analysis was used to identify the influencing factors for the prognosis of patients with cirrhotic ascites and infection. The receiver operating characteristic （ROC） curve was used to evaluate the diagnostic and prognostic efficacy of each indicator，and the Delong test was used for comparison of the area under the ROC curve （AUC）. Results The level of TREM-1 in ascites was significantly positively correlated with that in serum （r=0.50，P<0.001）. Compared with the improvement group，the non-improvement group had a significantly higher level of TREM-1 in ascites （Z=-2.391，P=0.017） and serum （Z=-2.544，P=0.011），and compared with the non-infection group，the infection group had a significantly higher level of TREM-1 in ascites （Z=-3.420，P<0.001），while there was no significant difference in the level of TREM-1 in serum between the two groups （P>0.05）. The level of TREM-1 in serum and ascites were significantly positively correlated with C-reactive protein （CRP），procalcitonin （PCT），white blood cell count，and neutrophil-lymphocyte ratio （r=0.288，0.344，0.530，0.510，0.534，0.454，0.330，and 0.404，all P<0.05）. The ROC curve analysis showed that when PCT，CRP，and serum or ascitic TREM-1 were used in combination for the diagnosis of cirrhotic ascites with infection，the AUCs were 0.715 and 0.740，respectively. The multivariate Logistic regression analysis showed that CRP （odds ratio ［OR］=1.019，95% confidence interval ［CI］： 1.001‍ ‍—‍ ‍1.038，P=0.043） and serum TREM-1 （OR=1.002，95%CI： 1.000‍ ‍—‍ ‍1.003，P=0.016） were independent risk factors for the prognosis of patients with cirrhotic ascites and infection，and the combination of these two indicators had an AUC of 0.728 in predicting poor prognosis. Conclusion The level of TREM-1 is closely associated with the severity of infection and prognosis in patients with cirrhotic ascites，and combined measurement of TREM-1 and CRP/PCT can improve the diagnostic accuracy of infection and provide support for prognostic evaluation.