A Clinical Study on the Prevention of Mild to Moderate Intermittent Asthma With Chinese Medicine Weiyang Yuping Fang

Inclusion Criteria: * Diagnosis of asthma according to GINA criteria with a documented history of at least 3 years prior to Visit 1 * Patients have asthma exacerbations every year * Meet the diagnostic criteria for mild to moderate asthma * Able to measure lung ventilation function according to ATS (American Thoracic Society) standards * Patients who have given written informed consent Exclusion Criteria: * Medical history of life-threatening asthma including intubation and intensive care unit admission * Any significant disease or disorder (e.g., cardiovascular, pulmonary other than asthma, gastrointestinal, hepatic, renal, neurological, musculoskeletal, endocrine, metabolic, malignant, psychiatric, major physical impairment) which, in the opinion of the investigator, may either put the patient at risk because of participation in the study, or may influence the results of the study, or the patient's ability to participate in the study * Pregnancy, breast-feeding or planned pregnancy during the study. * Participation in another clinical study or took other research drugs during the last 30 days prior to Visit 1 * Known or suspected hypersensitivity to study drugs or excipient * Suspected poor capability, as judged by the investigator, of following instructions of the study.