Abstract: OBJECTIVE To observe the prevention and treatment effect of bronchial asthma by the acupoint application of Baijiezi (Semen Sinapis) tufang， and the relationship between efficacy and skin irritation. METHODS The included bronchial asthma patients were applied during the dog days， all patients in the first year of the baseline stage were given low-dose medicine acupoints application on the control points of Fei shu (BL 13)， Xin shu (BL 15)， Ge shu (BL 17).In the second year， the patients were randomized into a control group， a placebo group and a experimental group， 30 cases in each one. The control group continued to apply low-dose medicine on the control acupoints， and the placebo group was given low-dose medicine acupoint application on Fei shu(BL 13)， Xin shu (BL 15)， Ge shu (BL 17). The experimental group were treated with normal does in Fei shu (BL 13)， Xin shu (BL 15)， Ge shu (BL 17). Observed the changes of asthma attack number， lung function and skin reaction after acupoint application treatment. RESULTS There was no significant difference in the number of asthma attacks between the baseline group， the placebo group and the control group. The number of asthma attacks was significantly reduced in the experimental group， the difference was statistical significant (P<0.01). There was no significant change in the number of asthma attacks between the placebo group and the control group. Compared with the baseline period， there was no significant difference in lung function (MMEF， FEF25， FEF50， FEF75) between the experimental group， the placebo group and the control group before the trial period. Compared with before the baseline period and the trial period， the lung function of the experimental group was significantly improved after the acupoint application treatment， the difference was statistical significant (P<0.05， P<0.01). But the lung function of the placebo group and the control group was not significantly improved， the difference was no statistical significant. Compared with baseline period acupoint application， the skin irritation was significantly enhanced in the experimental group of trial period， the difference was statistical significant (P<0.01).The difference in skin irritation between the placebo group and the control group has no statistical significant. CONCLUSION Baijiezi (Semen Sinapis) tufang acupoint application can effectively improve the small airway function of asthma patients， thus reducing the number of asthma attacks. The treatment effect is related to the skin irritation after the application.