Objective To clarify the efficacy and potential mechanism of Cordyceps militaris extract to nourish kidney yang. Methods SD rats were divided into normal, model, testicular tablet (0. 216 g / kg), and Cordyceps militaris extract high, medium, and low dose groups (0. 72, 0. 36 and 0. 18 g / kg, respectively) with 10 per group. Except for the normal group, all other groups were administered adenine (200 mg / kg) by gavage to establish a kidney yang deficiency rat model. Test drug administration was started on day 15 of model establishment for 28 consecutive days. ELISA were used to measure rat serum gonadotropin releasing hormone (GnRH), luteinizing hormone (LH), testosterone (T) and estradiol (E2) levels. HE staining was used to observe the morphology of kidneys, testes, epididymis, and seminal vesicle glands. Immunohistochemistry and Western blot were used to detect CYP19, CaM and CaMKⅡ expression in testes. CYP19 mRNA expression was detected in testes by RT-qPCR. Results Compared with the normal group, serum GnRH, LH and T levels of the model group were significantly reduced (P<0. 05), kidney, testis, epididymis and seminal vesicle gland tissues were all significantly damaged, and CYP19 expression in testes was reduced (P<0. 01). CaMKⅡ expression was increased significantly (P<0. 01). CYP19 mRNA expression was decreased significantly (P<0. 01). Compared with the model group, GnRH, LH and T contents in the high-dose Cordyceps militaris extract group were increased (P< 0. 05), tissue damage was relieved, CYP19 expression in testis was increased (P<0. 05), CaM and CaMKⅡ were decreased (P< 0. 05), and the CYP19 mRNA level was increased (P<0. 05). Conclusions Cordyceps militaris extract exerts a kidney yang effect by regulating CYP19 / CaM/ CaMKⅡ signaling.