Cardiogenic asthma is mostly caused by acute left heart failure, or acute pulmonary edema that resembles an asthma attack. In this case, the patient mostly has symptoms such as terminal breathing, pronounced wheezing, profuse sweating and irritability. The use of morphine can rapidly relieve the clinical symptoms and promote the reduction and absorption of pulmonary stasis. The mechanism is that morphine has the effect of dilating peripheral blood vessels, which can reduce the resistance of peripheral circulation and thus reduce the load on the heart. Morphine has a sedative effect that can reduce the patient’s irritability and anxiety, and it can also reduce the sensitivity of the respiratory center and weaken the symptoms of rapid and superficial breathing caused by reflexes. Therefore, morphine can be used for emergency treatment of cardiogenic asthma, and is a more effective drug.