Objective To investigate the therapeutic effect and underlying mechanism of Qishishenshu Capsule on renal fibrosis in mice with early diabetic nephropathy (DN). Methods A DN mouse model was established by multiple injections of streptozotocin. The mice were randomly divided into a normal group (NC), model group (DN), and Qishi group (QS) (0.9 g/(kg·d)), with eight mice in each group. Mice were gavaged continuously for 4 weeks, and fasting blood glucose (FBG) was measured weekly. Four weeks later, urinary albumin/creatinine (UACR), serum creatinine, and blood urea nitrogen were measured. Hematoxylin-eosin, periodicacid-Schiff, and Sirius red staining were used to analyze renal pathological changes. Real-time fluorescence quantitative reverse-transcription polymerase chain reaction was used to detect the mRNA levels of fibronectin (FN), collagen type I alpha 1 (Col1a1), and α-smooth muscle actin (αSMA). Immunohistochemistry and Western blot were performed to detect FN, collagen type I (Collagen I), collagen type III (Collagen III), α-SMA, Podocin, Nephrin, and transforming growth factor-β1/SMAD family member2/3 (TGF-β1/Smad2/3) pathway-related proteins. Results Compared with mice in the NC group, those in the DN group showed significantly higher levels of FBG and UACR (P<0.001), and mesangial hyperplasia, basement membrane thickening, and collagen deposition in the renal tissue. The mRNA levels of FN, Col1a1, and α-SMA were increased (P<0.05). Protein levels of Podocin and Nephrin were decreased (P<0.05). The levels of FN, Collagen I, Collagen III, α-SMA, and TGF-β1/Smad2/3 pathway proteins were increased (P<0.05). Compared with the DN group, the QS group’s level of UACR was decreased (P<0.05), their renal pathological injury was alleviated, and mRNA levels of FN, Collagen I, and α-SMA were attenuated (P<0.05); whereas their protein levels of Podocin and Nephrin were elevated (P<0.05). The levels of FN, Collagen I, Collagen III, α-SMA, and TGF-β1/Smad2/3 pathway proteins were also decreased (P<0.05). ConclusionsQishishenshu Capsule improved renal fibrosis in DN mice, probably through the inhibition of the TGF-β1/Smad2/3 signaling pathway.