Objective To investigate the effects of Chaihuang Yishen Granules on renal fibrosis in unilateral ureteral obstruction (UUO) mice and its underlying mechanisms. Methods Twenty-four 8-week-old male C57BL/6 mice were randomly divided into control group, model group, and low and high dose groups of Chaihuang Yishen Granules (6 in each group). In control group, only right kidney ureter was exposed and dissected. In model group, the UUO animal model was established by UUO. In low and high dose groups, mice were administered intragastrically at doses of 3.8 and 7.6 g/kg of Chaihuang Yishen Granules respectively,following the model group's method to establish the UUO model. After 7 days, the mice were euthanized and renal samples were collected. HE and Masson staining were used to observe pathological changes and fibrosis degree of the kidneys in each group, Sirius red staining was used to observe collagen deposition. The expression levels of α-smooth muscle actin (α-SMA), fibronectin (FN), type Ⅰ collagen (Col-Ⅰ), glycogen synthase kinase 3β (GSK-3β), and β-catenin related proteins were detected using Western blotting. Changes in A33 and GSK-3β, β-catenin mRNA levels were measured by RT-PCR. Additionally, a normal transformed C3H mouse kidney-1 (TCMK1) was used as control (normal group); an in vitro fibrosis model was established using TCMK1 stimulated with Transforming Growth Factor‑β (TGF‑β); and an in vitro drug model was established using TCMK1 treated with serum containing Chaihuang Yishen Granules. A33 was overexpressed in TCMK1 cells using a transfection with an A33 overexpression plasmid, and changes in fibrosis-related indicators and the expression of A33 and GSK-3β, β-catenin mRNA were observed. Results RT-PCR results showed that, compared with control group, A33 level was significantly increased in model group, while it was significantly reduced in both low and high dose groups of Chaihuang Yishen Granules (P<0.05). Western blotting showed that the expression levels of fibrosis-related factors such as α-SMA, FN, Col-Ⅰ in model group were significantly higher than those in control group (P<0.05); while compared with model group, the expression levels of α-SMA, FN, Col-Ⅰ in low and high dose groups of Chaihuang Yishen Granules were significantly lower (P<0.05). HE, Masson, immunohistochemical staining results showed that model group had severe kidney structural damage, significant increase in collagen deposition, and significantly higher expression levels of GSK-3β and β-catenin proteins compared with those in control group (P<0.01). In contrast, low and high dose groups of Chaihuang Yishen Granules had good kidney structure, significant improvement in kidney damage and fibrosis, and significantly lower expression levels of GSK-3β and β-catenin proteins compared with those in model group (P<0.05). In vitro experiment results confirmed that, compared with normal group, A33 overexpression promoted the upregulation of fibrosis-related factors in TCMK1 cells, significantly increase the expression of downstream target genes GSK-3β and β-catenin mRNA in the Wnt/β-catenin signaling pathway (P<0.05), and A33 overexpression reversed the cellular fibrosis changes downregulated by the serum containing Chaihuang Yishen Granules (P<0.01). Conclusion Chaihuang Yishen Granules significantly improve renal fibrosis in UUO mice by downregulating the A33/Wnt/β-catenin signaling pathway, suggesting that A33 may be a potential therapeutic target for renal fibrosis.