The fallowing are the result of the experimental studies of KH-304 on the penile nitric oxide synthase (NOS) activity, SOD and the level of blood testosterone in old rat. KH-304 was tested for the expression and activity of eNOS, nNOS, SOD/Mn, caveol in-1, 3 in penis of old-rat. The penile expression level of the five enzyme were increased significantly after oral administration of the KH-304 100mg/kg for 100ays and the concentration of testosterone in the blood were increased. In vitro, the effect of SOD and free radical scavenging were increased significantly. Conclusively, KH-304 is capable of improving of sexual ability in old-rat.