Objectives The purpose of this clinical trial was evaluate the safety and efficacy of Mahwangjeongcheon-tang (MJT). Methods Twenty six volunteers were recruited as subjects. They were divided into two groups, which were MJT test group and placebo group. The investigated items related to the safety were the weight, the results of renal function and liver function. The investigated items related to the efficacy are the results of the spirometer, the clinical asthma measurement scale in oriental medicine-V (CAMSOM-V) and the quality of life questionnaire for adult Korean asthmatics (QLQAKA). Results There are no difference in the weight, the results of the renal functions and the liver functions between MJT test group and placebo group. There are the some differences in the result of the questionnaires related to the efficacy between MJT test group and placebo group. The significant difference were observed in the CAMSOM-V at the 4th visit. Conclusion MJT is the safe and effective herbal prescription that is useful to the asthma patients.