〔Abstract〕 Objective To explore the correlation between small intestinal bacterial overgrowth (SIBO) and cognitive impairment in patients undergoing peritoneal dialysis (PD). Methods60 PD patients and 46 non-dialysis patients with end-stage renal disease (ESRD) were included in this study. SIBO was detected by lactulose hydrogen methane breath test (LHMBT). The cognitive function levels of the subjects were evaluated using the Montreal cognitive assessment (MoCA) and mini-mental state examination (MMSE). The emotional states of the patients were assessed by self-rating anxiety scale (SAS) and self-rating depression scale (SDS). The gastrointestinal symptoms were evaluated using gastrointestinal symptom rating scale (GSRS). According to the results of LHMBT, the PD patients were further divided into two subgroups: SIBO-positive and SIBO-negative. The general conditions, laboratory data, and scores of each scale were compared between the two groups. Furthermore, according to the MoCA scores, the PD patients were divided into two groups: those with normal cognitive function and those with cognitive dysfunction. The positive rates of SIBO between the two groups were compared. Binary Logistic stepwise regression was used to explore whether SIBO was an independent risk factor for cognitive impairment in PD patients. At the same time, other independent influencing factors for cognitive impairment in PD patients were analyzed. Result s The positive rate of SIBO in PD patients was 40%. Among them, the positive rate of SIBO in the group with normal cognitive function during peritoneal dialysis was 27.27%, and the positive rate of SIBO in the group with cognitive dysfunction during peritoneal dialysis was 55.56%. There was a statistically significant difference in the positive rate of SIBO between the two groups ( P =0.026). Further analysis by multivariate Logistic stepwise regression showed that in addition to age ( OR=1.118, 95% CI 1.007-1.242, P =0.037), educational attainment（ OR=0.655，95% CI 0.442-0.972， P =0.036）, and hemoglobin （ OR=0.946，95% CI0.895-0.998， P =0.044）, SIBO （ OR=7.613，95% CI1.160-49.979， P =0.034）was also an independent risk factor for cognitive impairment in PD patients. ConclusionThe incidence of SIBO in PD patients is relatively high and is associated with multiple factors, among which SIBO may be closely related to cognitive dysfunction in PD patients.