Asthma, a chronic lung disease which causes severe problem in breathing. The asthma cause due to lung airway constriction by triggers, such as allergic reactions to dust or pollen. The asthma never diagnose at early stage since symptoms such as coughing confuse with cold. The Asthma only diagnose when shortness of breath occur and it causes an examination by a physician. In this paper, we propose a non-invasive way to diagnose asthma at early stage via bio magnetic signal acquired from a person lung. The mucus in airway of lung clogs airway during constriction. The Giant magnetoresistance (GMR) sensor place on lung region and bio-magnetic emission from mucus in lung acquire. The biomagnetic signal of mucus in lung constricted airway change due to mucus normal and dynamic condition. The constricted lung airway cure by Ventolin entolin inhaler, which makes constricted muscle to relax and provide airflow. The mucus accumulation and mucus flow provide varying bio-magnetic emission. The bio-magnetic emission change correlate with asthma through RADWT subband energy level. The RADWT subband energy level and airflow meter test model with linear regression for lung airway opening and asthma diagnosis.