Objective To observe the morphologic changes of rat peritoneum tissue in different age groups, so as to explore the age-related molecular and pathology characteristics. Methods Eighteen male SD rats were evenly randomized into three groups:1-month group (the juvenile group); 8-month group (the youth group); and 18-month group (the elderly group). The morphological changes of parietal peritoneum were observed by Hematoxylin-Eosin and β-gal staining. The peritoneal thickness, peritoneal mesothelial cells and blood vessel count under unit area were analyzed semi-quantitatively. The expressions of transforming growth factor-beta 1(TGF-β1) and krüppel like factor 15(KLF15) mRNA or protein in the rat mesenteric tissues were evaluated by RT-PCR and Western blotting analysis. Results The peritoneum gradually thickened with the increase of age, accompanied by reduced peritoneal mesothelial cells and increased interstitial vascular proliferation (P<0.05). The expression of TGF-β1 was gradually increased (P<0.05) and that of KLF15 was decreased (P<0.05) at mRNA and protein levels, and the expression of TGF-β1 was negatively associated with KLF15. Conclusion It is speculated that TGF-β1 may play a role in promoting the peritoneal aging process, while the KLF15 factor may inhibit the peritoneal senescence.