BACKGROUND: The aim of this study is to investigate the effects of Lycium chinense Miller fruit and its representative constituent betaine on reduction of immobility time and blood parameters in balb/c mice. METHODS AND RESULTS: We investigated the immobility time and the changes in aspects of blood biochemical parameters by the administration of L. chinense Miller fruit and its representative constituent betaine, after the forced swimming test. The immobility time was significantly reduced about 41.3% and 53.6%, respectively, in the animal of L. chinense Miller fruit and its representative constituent betaine-administrated group for 7 days, in comparison with that of the control group. The level of blood urea nitrogen was significantly decreased in L. chinense Miller fruit and its representative constituent betaine-treated group compared with the control group (P < 0.05), respectively. In addition, the interlukin-2 levels of mice in L. chinense Miller fruit and betaine treated group was increased compared with the control group. CONCLUSION: These results indicate that L. chinense Miller fruit and betaine might be helpful in the immune function improvement, enhance physical stamina, and fatigue recovery.