Abstract: Objective To detect the expression of molecular marker protein and miR-200c in the mesothelial cells of the peritoneal dialysate effluent fluid of peritoneal dialysis (PD) patients, and to investigate the association between miR-200c and human peritoneal mesothelial cell (HPMC) epithelial-mesenchymal transition(EMT). Methods Twelve patients recently given continuous ambulatory peritoneal dialysis (initial PD group) and 16 patients undergoing peritoneal dialysis for more than 6 months (PD over 6 months group) were randomly chosen for the isolation, culture and identification of effluent cells. Real-time PCR and Western blotting were used to detect the expression levels of miR-200c, and the levels of four cellular marker proteins:E-cadherin, vimentin, fibronectin (FN) and COL-1, in effluent cells. Results Cells isolated from effluents of dialysis fluid were identified as HPMCs. The morphology of effluent cells varied according to how long patients undergoing PD. The relative expression of miR-200c in the effluents HPMCs of the initial PD group was (7.546±0.341), and the relative expression of miRNA-200c in the effluent HPMCs of the PD over 6 months group was (1.701±1.070)(P<0.01). The level of E-cadherin mRNA and protein expression was significantly lower in the PD over 6 months group than in the initial PD group, while vimentin, FN and COL-1 mRNA and protein expression levels were significantly increased in the PD over 6 months group as compared with those in the PD initial group. Conclusions Cells isolated from effluents of dialysis fluid were identified as HPMCs, and the expression of miRNA-200c in HPMCs were confirmed. With the prolongation of PD time, miR-200c expression was significantly reduced and associated with EMT, suggesting that miR-200c may be associated with peritoneal fibrosis.