Objective: To study the molecular mechanism of Yangjing Capsule (YC) promoting the proliferation of mouse spermatogonia stem cells (SSCs). Methods: YC extract of different concentrations were added to SSCs for 48 h, and the proliferation activity of cells was detected by CCK-8, the cell cycle was detected by flow cytometry, the activity of Cyclin D1 promoter was detected by luciferase reporter assay, and the expression of Cyclin D1 was detected by qRT-PCR and immunofluorescence. Then the blocking experiments were carried out, siRNA-Cyclin D1 was added before the treatment of YC, and the proliferation activity, the cell cycle of cells, as well as the activity of Cyclin D1 promoter and the expression of Cyclin D1 were detected by the same methods. Results: The low, medium and high dose of YC could promote the proliferation of SSCs, increase the proportion of S-stage cells, enhance Cyclin D1 promoter activity, and promote the expression of Cyclin D1. Blocking experiments showed that pre-treatment of siRNA-Cyclin D1 could reduce the proliferation activity of SSCs, reduce the proportion of S-phase cells, decrease Cyclin D1 promoter activity, and inhibit the expression of Cyclin D1. Conclusion: YC extract promotes proliferation of mouse spermatogonia stem cells through regulating Cyclin D1 promoter and improving the transcription and translation of Cyclin D1.