Objective To investigate the protective effect and mechanism of action of Coptis chinensispolysaccharide (CCPW) on the kidney in a streptozotocin (STZ)-induced rat model of diabetes. Methods A Sprague-Dawley (SD) rat model of diabetes was established by intraperitoneal injection of STZ (60 mg/ kg). The diabetic rats wererandomly divided into disease model, high-dose CCPW (300 mg/ kg/ d), low-dose CCPW (100 mg/ kg/ d) and losartan(30 mg/ kg/ d) groups, containing 10 rats each. A group of 10 non-diabetic SD rats was included as the normal controlgroup. The rats were intragastrically administered the drugs once a day continuously for 8 weeks. At the end of the 8-weekadministration period, the effects of CCPW on body weight, kidney-to-body weight ratio, serum BUN and SCr levels, 24-hour urine protein levels, pathological changes in renal tissue, changes in the activity of the antioxidant enzymes SOD,CAT and GSH-Px, MDA content, and changes in the expression of IL-6, hs-CRP and TNF-α were observed in the diabeticrats. Results Compared with the disease model group, the CCPW-treated diabetic rats demonstrated a significant increasein body mass and a significant decrease in the kidney-to-body weight ratio. Significant decreases in serum BUN and SCrlevels as well as the 24-hour urine protein level were also observed. Pathological changes in the renal tissues of CCPW ratswere also less apparent, when compared with the untreated disease model animals. SOD, CAT and GSH-Px activity in renaltissues was significantly elevated, while MDA content and IL-6, hs-CRP and TNF-α expression in the serum weresignificantly reduced in the CCPW-treated groups. Conclusions CCPW may have a protective effect on the renal tissue of diabetic rats, possibly through its inhibition of oxidative stress and inflammation.