Objective To investigate the interference and associated mechanism of hnman tissue kallikrein (HK) gene on renal interstitial fibrosis in rats with 5/6 nephrectomy. Methods Human kallikrein cDNA was packed in a recombinant adeno-associated virus(rAAV)-based plasmid vector. The rAAV-HK was produced by transfection in 293 cells. Twenty-four male Wistsr rats were divided into sham operation and operation groups. The rats with 5/6 nephrectomy were randomly divided into simple operation, control and experiment groups. The rats in experiment group received single dose rAAV-HK via the tail vein with 1×1011 pfu. Before nephrectomy and every month after surgery until the rats were sacrificed, the caudal arterial pressure was measured using tail cuff blood pressure determinator. Three months after HK gene delivery, the rats were sacrificed. The expression of HK in rats was assessed by RT-PCR, Western blot and enzyme-linked immunosorbent assay (ELISA). The pathological changes of renal interstitium were evaluated by Masson stainning, and the distribution of bradykinin B2 receptor (BKB2R) and angiotensin Ⅱ typel receptor (ATIR) was examined by immunohistochemistry. The expressions of BKB2R, AT1R, p-MAPK protein in renal tissue were detected by Western blot. Results Three months after HK gene delivery, the systolic blood pressure of experiment group was significantly decreased compared with the control group [(163±13) nun Hg vs (217±16) mm Hg, P<0.01](1 mm Hg=0.133 kPa). Compared with sham rats, the rats in simple operation group and control group had much more renal interstitial collagen deposition and more serious fibrosis performance, but renal interstitial collagen deposition and fibrosis were significantly ameliorated in the rats of experiment group. In addition, the tubulointerstitial injury index of HK transgenic rats was significantly lower than that of the rats in control group (1.33±0.73 vs 3.01±0.62, P<0.01). Up-regnlating expression of bradykinn B2 receptor protein and down-regulating expression of AT1 receptor and p-MAPK protein were found in renal tissues of experimental group after three months (P<0.05). Conclusion HK gene delivery significantly alleviates renal interstitial fibrosis in rats with 5/6 nephrectomy through regulating the expression of bradykinin B2 receptor, AT1 receptor and p-MAPK in renal tissue.