Introduction: Chronic obstructive pulmonary disease (COPD) is a common disease characterized by persistent airflow obstruction with an enhanced chronic inflammatory response in the airways and the lung to noxious particles or gases. Oxygen deficiency (hypoxia) causes an increase in Reactive Oxygen Species (ROS). ROS can be neutralized with antioxidants, one of which is Bael leaf. Objective: To evaluate the antibacterial activity of plant leaf extract against the common isolated bacteria [Psuedomonas aeruginosa]. To know the Relaxant effect of bael leaf (Aegle marmelos) on oxidative stress in Sprague Dawley lung induced chronic systemic hypoxia. Methods: The study was conducted in SIMATS and Sri Akilandeswari Pharma College for the period of Six months from April 2020 to September 2020. 110 sputum samples were analysed for testing antibacterial activity. Neutralization of ROS has been determined by DPPH radical scavenging method. Contractile effect was done by the Organ bath method. Results: Among gram negative bacteria predominantly Pseudomonas aeruginosa is the commonest bacteria. The other important organisms are Klebsiella pneumoniae, E. coli, Acinetobacter species. Antibiotics showing high activity against Pseudomonas aeruginosa are Piperacillin tazobactam, Carbapenemase, and Quinolones. mucA gene mutation of P. aeruginosa could be used as predictors to identify poor prognosis in COPD patients. Analysis of antioxidant activity in Aegle marmelos shows 79.8% of reductions in DPPH free radicals for 100μg/ml. The minimum inhibitory concentration (MIC) value of the methanolic extract is around 256 μg/ml. 1mg/ml and 2mg/ml doses of the methanolic extract of this plant produced a positive relaxant effect in an isolated mouse bronchial rings, respectively. Conclusion: Methanolic extracts elicited the antagonistic effect against histamine and also relaxed the histamine-induced contractions, it can be concluded that relaxations induced by A. marmelos in mouse broncheal chain were due to the depression of H1-receptors. This study shows that Aegle marmelos can be effectively used in the treatment of COPD disorders.