Background: Er-Xian Decoction (EXD) is one of the traditional Chinese medicine (TCM) with unique effect on osteoporosis, menopausal syndrome and delayed puberty in China for many years. Objective: We aim to evaluate the potential activity of starting hypothalamic-pituitary-testicular (HPT) axis of male rats with delayed puberty. Materials and Methods: Delayed puberty model of male Sprague-Dawley (SD) rats were established with soy isoflavones (90 mg·kg -1) and were treated by EXD extract at doses of 5, 10 g·kg -1 or Testosterone undecanoate (TU) for 8 weeks. Body weight, body length, testis weight, T, E 2 and luteinizing hormone (LH) in serum, gonadotropin releasing hormone (GnRH) in hypothalamus, follicle stimulating hormone (FSH) and LH in pituitary gland were determined by ELISA. Immunohistochemistry was used to detect LH in pituitary gland. Results: Soy isoflavones could significantly decrease body weight, body length, testicular organ coefficient T in serum, GnRH in hypothalamus, FSH and LH in pituitary gland. Both of EXD and TU could improve the condition. E 2 and LH in serum of all groups were non-significance of difference (P > 0.05). The immunohistochemical results were well consistent with LH in pituitary gland. Conclusion: The results of the present research indicate that EXD extract is effective to start the HPT axis in puberty and can significantly improve sexual developmental inhibition caused by soy isoflavones.