Abstract: Peritoneal dialysis-related peritonitis is a common complication of patients receiving peritoneal dialysis. However, peritonitis caused by anaerobic infection is rare. This article was reported a 44-year-old female patient who had undergone maintenance peritoneal dialysis for more than 4 years. She was admitted due to abdominal pain, diarrhea, and turbid peritoneal fluid after being diagnosed with peritoneal dialysis-related peritonitis. Repeated peritoneal fluid culture tests yielded negative results. After ineffective anti-infection treatment, the possibility of peritoneal dialysis-related refractory peritonitis was considered. Metagenomic next-generation sequencing （mNGS） pathogenic examination revealed the presence of Bacteroides thetaiotaomicron infection. She was recovered and discharged after combined use of metronidazole combined with imipenem and cilastatin sodium for 18 d. No recurrence of peritonitis was observed during follow-up. The diagnosis and treatment of this case prompt that attention should be paid to peritoneal dialysis-related peritonitis caused by anaerobic bacterial infection. mNGS can be applied in the routine examination of peritoneal dialysis-related peritonitis, aiming to improve the detection rate of pathogenic microorganisms, promptly select appropriate antibiotics for anti-infection therapy and enhance clinical prognosis of patients.