To explore the predictive value of controlling nutritional status (CONUT) score and dialysis age for peritoneal dialysis-associated peritonitis (PDAP). This study was a follow-up study. Patients with end-stage renal disease who received peritoneal dialysis (PD) for the first time in the Department of Nephrology, the Third Affiliated Hospital of Suzhou University from January 2010 to December 2020 were enrolled in the study. Patients were divided into non-peritonitis group, mono group (only once PDAP occurred in one year) and frequent group (twice or more PDAP occurred in one year) according to the occurrence and frequency of PDAP during follow-up. The demographic, clinical and laboratory data of patients were collected, and the body mass index and CONUT score were recorded after half a year. Cox regression analysis was used to screen the relevant factors, and receiver operating characteristic (ROC) curve was used to analyze the predictive value of CONUT score and dialysis age for PDAP. A total of 324 PD patients were included, with 188 males (58.0%) and 136 females (42.0%), and aged［（，）］48 (37, 60) years old. The follow-up time was 33 (19, 56) months. PDAP occurred in 112 patients (34.6%), including 63 patients (19.4%) in mono group and 49 patients (15.1%) in frequent group. Multivariate Cox regression analysis showed that half-year CONUT score (=1.159, 95%: 1.047-1.283, =0.004) was a risk factor for PDAP, and the baseline CONUT score (=1.194, 95% 1.012-1.408, =0.036) was a risk factor for frequent peritonitis. The area under ROC curve of baseline CONUT score combined with dialysis age in predicting PDAP and frequent peritonitis was 0.682 (95%: 0.628-0.733) and 0.676 (95%: 0.622-0.727), respectively. CONUT score and dialysis age have certain predictive value for PDAP, and the predictive value of combined diagnosis is higher, which may be used as a potential predictor for PDAP in PD patients.