A clinical and experimental study to evaluate effects of the Jianpi Yiqi (JPYQ, Invigorate the spleen and supplement the Qi) prescription was conducted, in contrast to 51 cases treated with transfer factor. The results showed that there were statistically significant differences between two groups for therapeutical effects (P < 0.005). In the experimental group, the effective rate and the total effective rate were respectively 75% and 92.1; while in control group, 8% and 72%. Measuring immunoglobulin (IgG), both groups were increased, but the experimental group was higher than that of control (P < 0.001). The inactivation in oxygen free radicals of JPYQ was determined by electron spin resonance (ESR) in vitro. When the concentration was 5%, the clearance rate of the more reactive hydroxyl radical (.OH) was 78%, and superoxide radical (O2.-) was 38%. Whether direct dissolution or dissolution combined with dialysis was performed, there was superoxide dismutase (SOD) activity. In addition, the relationship between infantile repetitive respiratory infection with Spleen Qi Deficiency and free radicals were discussed.