Objective To investigate the therapeutic effect of baicalin at different doses administered for different periods of time in the treatment of renal interstitial fibrosis in rats with unliateral ureteral obstruction (UUO) and related mechanisms. Methods Sixty-four Sprague-Dawley rats were randomly divided into sham-operation, model, low-dose baicalin, and high-dose baicalin groups, and each group was further randomly divided into 7-day and 14-day groups (n=8 each). Left ureteral ligation was used to establish the rat model of UUO. Hematoxylin and eosin staining was used to observe the pathological changes in the kidney. ELISA was used to measure the serum levels of transforming growth factor-β1 (TGF-β1), Notch1, and Jagged1. Immunohistochemistry was used to measure the expression of TGF-β1 and Notch1. The Pearson correlation analysis was used for correlation analysis. Results Hematoxylin and eosin staining showed inflammatory cell infiltration and edema in renal interstitium, tubular dilation and structure disorder, degeneration and necrosis of renal tubular epithelial cells, and a basically normal structure of the glomeruli on days 7 and 14 in the model group, and these lesions were alleviated in the low-and high-dose baicalin groups. Compared with the sham-operation group, the model group had a significantly higher serum level of TGF-β1 and a significantly higher number of TGF-β1-positive cells in renal tissues on days 7 and 14 (P<0.05). Compared with the model group at the same time points, the high-and low-dose baicalin groups had a significantly lower serum level of TGF-β1 and a significantly lower number of TGF-β1-positive cells in renal tissues on days 7 and 14 (P<0.05). The serum level of Jagged1 showed no significant differences between any two groups on days 7 and 14 (P>0.05). The serum level of TGF-β1 was positively correlated with that of Notch1 (r=0.650, P<0.01), and the serum level of Notch1 was positively correlated with that of Jagged1 (r=0.727, P<0.01). TGF-β1 level in renal tissues was also positively correlated with the number of Notch1-positive cells (r=0.743, P<0.01). Conclusions Baicalin can alleviate renal interstitial fibrosis in UUO rats, probably by inhibiting Notch1 signaling pathway and the expression of TGF-β1.