OBJECTIVE To explore on prevention and treatment of severe asthma with reinforcing the Kidney and invigoration the Spleen Principle (RKISP) and its mechanism. METHODS Patients were treated with steroid aerosol (as control group), and both steroid aerosol and RKISP (as test group) respectively. RESULTS The markedly effective rate of the test group was higher than that of the control group, the doses of beta-analeptic and the side-effect rates of the test group were lower than that of the control group, the pulmonary function of the test group was more remarkably improved. After treatment, the T cell hyperplasia response to specific allergen, the basophilic cell releasing capacity, the serum IgE and eosinophil of the test group were all reduced more obviously than those of the control group. In the control group, the neutrophil increased and the neutrophil phagocytic capability as well as the function of adrenal cortex were declined. While in the test group, the neutrophil phagocytic capability was raised, the neutrophil and the function of adrenal cortex had no significant changes. CONCLUSIONS RKISP cooperated with steroid in relieving attack of asthma, and it was more important for it to display an obvious modulation action on immune and neuroendocrine system.