Objective To observe the pathological changes in asthma after being treated with pulmonary surfactant (PS) dripped into the airway. Methods The asthmatic model was set up using guinea pigs immunized against ovalbumin. The pathological changes of bronchioles from five asthmatic animals and five treated ones were compared thirty minutes after the dripping of 0.3 ml PS into the airway. Results There were marked smooth muscle spasm, inflammatory cell infiltration and a large amount of exudate in the airway lumen in the asthma group. After being treated with PS, the inflammatory exudate disappeared and cell infiltration was alleviated. Conclusions Exterior PS could relieve spasm of bronchiole smooth muscle and alleviate airway inflammation.