OBJECTIVE To explore the therapeutic effect of Heirong Kidney-Tonifying Granule (HKTG) on busulfan-induced dyszoospermia in mice, and its mechanism in regulating testicular spermatogenesis. METHODS Forty-eight male mice were randomly divided into six groups of an equal number: blank control (BC), negative control (NC), HKTG-1, HKTG-2, HKTG-3 and HKTG-4. The model of dyszoospermia was established in the latter five groups by intraperitoneal injection of busulfan at 40 mg/kg and, 30 days after modeling, the mice in the BC and NC groups were given gavage of normal saline, and those in the latter four groups treated with HKTG + pilose antler at 400 mg/kg/d, HKTG + pilose antler at 800 mg/kg/d, HKTG + black ants at 400 mg/kg/d and HKTG + black ants at 800 mg/kg/d, respectively, all for 5 consecutive weeks. The mean body weight of the mice was recorded daily, and their testes weighed after treatment. The microstructure of the testis tissue was detected by HE staining, and the localization and expression of spermatogenesis markers in the testis were determined by immunofluorescence staining. RESULTS The mice in the BC and NC groups showed no statistically significant difference from those in the HKTG groups in the body weight and daily body weight gain (P > 0.05). Compared with the NC mice, the animals in the HKTG-1 group exhibited significantly increased testis weight (P < 0.05), and those in the HKTG-1 and HKTG-1 groups presented a large number of germ cells in the seminiferous tubules, including deformed sperm cells in the lumen, and some seminomatogonia in the seminogenic tubules, but almost no deformed sperm cells. The expressions of the total germ cell marker gene Ddx4, spermatogonial cell marker gene Dazl, spermatic cell marker gene Sycp3 and sperm cell marker gene Tnp1 were significantly upregulated (P < 0.05) while that of the Sertoli cell marker gene Sox9 downregulated (P < 0.05) in the HKTG-1 group. The number of Sertoli cells in the HKTG-1 group was remarkably reduced (P<0.05), corresponding to the increased number of germ cells in the HKTG-1 group. There were no significant changes in the relative expressions of the DDX4, Dazl, Sycp3 and Tnp1 genes, nor in the number of Sertoli cells in the HKTG-3 and HKTG-4 groups. The expressions of meiosis-related genes Meioc, Stra8 and Spo11were markedly upreguated in the HKTG-1 group, indicating significantly improved spermatogenesis in the testis tissue of the mice. CONCLUSIONS HKTG improves the function of spermatogenic cells and increases sperm production in the testis tissue of mice by promoting meiosis.