Objective To study the effect of muskmelon juice on immune function of aged mice induced by D-galactose. Method Fifty male Kunming mice were randomly divided into five groups:normal control,aged model and three muskmelon juice (quadruple-diluted,double-diluted and stock juice) groups. The mice in aged model and three muskmelon juice groups were injected subcutaneously with D-galactose at dose of 200 mg/kg?d ,and the normal control with the normal saline of equal volume. The mice in three muskmelon juice groups were treated by intragastric administration twice daily with quadruple-diluted solution,double-diluted solution and stock liquid of muskmelon juice respectively,and the mice in normal control and aged model group with distilled water. Four weeks later,spleen and thymus were weighted,and the immunoglobulim and complement in serum were estimated. Results The thymus index of mice in aged model groop was much lower as compared with normal control. After administration with muskmelon juice,the thymus index was increased and the difference between stock juice and aged model group was significant. As compared with normal control,the serum IgG,IgM,C3,C4 contents of aged model were significantly lowered,but those in muskmelon juice group was increased. The IgG,C3,C4 contents of double-diluted and stock juice group were significantly higher than those of aged model. The spleen index and serum IgA contents fluctuated with same tendency. Conclusion Muskmelon juice can relieve the regression of immune organs in aging process and improve the immune function,suggesting to be effective in anti-aging process.