Objective To understand the distribution characteristics and antimicrobial resistance of pathogenic bacteria isolated from peritoneal effusion specimens from member units of China Antimicrobial Resistance Surveillance System (CARSS). Methods Bacterial strains isolated from peritoneal effusion specimens of CARSS member units from January 1, 2020 to December 31, 2024 were analyzed. Repetitive strains of the same bacteria from the same patient were excluded, only the first strain was retained for analysis. Antimicrobial susceptibility testing results were assessed according to the standards of American Clinical and Laboratory Standards Institute (CLSI). Results A total of 373 238 bacterial strains were isolated from peritoneal effusion specimens from CARSS member units in 2020-2024, 39.2% were Gram-positive and 60.8% were Gram-negative strains. The top 10 isolated bacteria were Escherichia coli (30.3%), Klebsiella pneumoniae (9.3%), Enterococcus faecium (7.6%), Staphylococcus epidermidis (5.4%), Enterococcus faecalis (5.3%), Pseudomonas aeruginosa (4.8%), Staphylococcus aureus (4.2%), Enterobacter cloacae (2.6%), Staphylococcus haemolyticus (2.4%), and Acinetobacter baumannii (2.3%). Among Staphylococcus aureus and coagulase negative Staphylococcus, the detection rates of methicillin-resistant strains (methicillin-resistant Staphylococcus aureus ［MRSA］ and methicillin-resistant coagulase negative Staphylococcus ［MRCNS］) were 27.9%-32.1% and 70.6%-72.9%, respectively. Resistance rates of methicillin-resistant strains to most antimicrobial agents were higher than methicillin-sensitive strains, while no strain was found to be resistant to vancomycin and teicoplanin. Among Enterococcus spp., Enterococcus faecium had higher resistance rates to most tested antimicrobial agents than Enterococcus faecalis. The resistance rates of Enterococcus faecalis to vancomycin and teicoplanin were 0.2%-0.4% and 0.3%-0.7%, respectively. The resistance rates of Enterococcus faecium to teicoplanin and vancomycin were 0.6%-5.7% and 0.7%-4.2%, respectively, both showing significant increase trends. The detection rates of carbapenem-resistant Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa were 11.1%-13.8%, 49.1%-56.1% and 11.8%-14.4%, respectively, all showing downward trends. Detection rates of carbapenem-resistant Escherichia coli were 1.9%-2.1%; resistance rates of Enterobacter cloacae to imipenem and meropenem were 5.9%-8.0% and 6.2%-8.1%, respectively; and resistance rates of Citrobacter freundii to imipenem and meropenem were 4.3%-10.9% and 3.9%-8.8%, respectively; all showing upward trends. Conclusion The number of clinical isolates detected from peritoneal effusion presents an increasing trend. Detection rates of most major antimicrobial-resistant strains present decreasing trends, while the detection rates of carbapenem-resistant Escherichia coli and vancomycin-resistant Enterococcus faecium have risen. Resistance rates of Enterobacter cloacae and Citrobacter freundii to carbapenem antibiotics have increased, which should be closely observed and given high priority, so as to avoid the spread within hospital.