Abstract: Objective To investigate the clinical characteristics and peritoneal function changes in chronic kidney disease （CKD） patients undergoing long-term peritoneal dialysis （PD）, and to evaluate the diagnostic utility of normalized protein catabolic rate （nPCR） in assessing dialysis adequacy in this population. Methods CKD patients receiving continuous ambulatory peritoneal dialysis （CAPD） at Dongguan Tungwah Hospital from 2009 to 2022 were selected, and divided into long-term and short-term dialysis groups. The long-term dialysis group was further categorized into high and low peritoneal equilibration test （PET） subgroups according to the average D/Pcr from PET. Intergroup differences were compared. The trend of solute transport was analyzed using the Friedman’s test, while Spearman’s correlation and receiver operating characteristic （ROC） curve analysis were employed to assess the correlation between nPCR and dialysis adequacy, and the diagnostic performance of nPCR, respectively. Results Among long-term dialysis patients, those in the high PET subgroup exhibited lower levels of serum albumin and nPCR, but higher creatinine clearance index （Ccr） （all P < 0.05）. The D/Pcr showed a downward trend followed by an upward trend over the first five years of dialysis （all P < 0.05）. nPCR was positively correlated with Ccr （r_s=0.305, P < 0.05） and urea clearance index （Kt/V, r_s=0.288,P < 0.05）, and negatively correlated with D/Pcr （r_s=-0.417, P < 0.001）. The area under the ROC curve for nPCR in diagnosing dialysis adequacy was 0.68 （P < 0.05）. Conclusion In CKD patients with long-term peritoneal dialysis, peritoneal function tends to decline initially and then improve. nPCR can serve as a nutritional indicator for evaluating dialysis adequacy.