Tonic Chinese prescriptions are widely used in daily foods to improve health in Taiwan. Huang Qi Liu Yi Tang (HQLYT) is one such tonic Chinese prescription. In this study, the immuno-enhancement effects of HQLYT tonic were explored using an in vitro splenocyte proliferation assay and by evaluating improvements in cyclophosphamide-induced leucopenia in a BaLb/c mice model. HQLYT is composed of Radix Astragali, licorice, and jujube, and extracted in boiling water. The contents of glycyrrhizin and formononetin were used as bioactive markers to control the quality of the HQLYT water extract, at 7.26+/-0.04mg/g and 112.07+/-0.08 micro g/g, respectively. In the in vitro assay, HQLYT (12.5 micro g/ml) showed better immuno-enhancing effects than Radix Astragali, licorice, or jujube alone, and enhanced the survival rate of splenocytes by 88%. Moreover, HQLYT significantly enhanced the cytotoxic effects of natural killer cells of splenocytes against YAC-1 cells. The BaLb/c mice were fed HQLYT once a day for 14 days. After oral treatment with HQLYT 400mg/kg body weight (BW), the IL-2 release in BaLb/c mice and the natural killer cell activity of the splenocytes were both enhanced, and the WBC level of cyclophosphamide-induced leucopenic mice was improved by treatment with 400mg HQLYT/kgBW. HQLYT significantly delayed the decline in the WBC level and affected a faster recovery of the WBC level back to a normal status. In summary, HQLYT enhanced immunologic functions in both in vitro and in vivo studies. These results offer scientific evidence to prove the efficacy of this tonic Chinese prescription.