After randomly dividing 45 elderly males with Kidney-Yang Deficiency into Zhuchun Pill (ZCP) group and placebo (starch capsule) group by single blind method, and treating them for 3 months, we found that ZCP could greatly improve the main symptoms of Kidney-Yang Deficiency, P < 0.01 by comparison with control group: the 3H-TdR lymphocyte transformation (3H-TdR LCT) rate, level of serum C3, IgA, IgD, IgG & IgM went up (P < 0.01); contents of plasma adrenocortical hormone (ACTH), testosterone (T) and cyclic adenosine monophosphate (cAMP) increased (P < 0.01-0.001): the level of superoxide dismutase (SOD) in serum also increased while lipid peroxide (LPO) in plasma decreased (P < 0.01). But for control group, there were no remarkable changes after treatment, so it revealed that the improvement of Kidney-Yang Deficiency by ZCP is realized through regulating the organism's immunity and endocrine function as well as through scavenging the free radical agents.