Ambroxol hydrochloride is a mucus dissolving agent developed by bringer Ingelheim company in Germany. It was first listed in Germany in the early 1980s, and then in France, Italy, Japan, Spain and many other countries. It is a new generation of mucus dissolving agent. It can improve expectoration, promote pulmonary surfactant, airway secretion and ciliary movement. In clinic, it can regulate the secretion of mucus and mucus, activate cilia swing, dilute sputum easily, strengthen mucus outward transportation, and discharge easily. It can also promote the synthesis of pulmonary surfactant to maintain alveolar tension and ensure lung function index; It can promote the penetration of antibiotics into tissues to increase the concentration and enhance the bactericidal effect; Antioxidant, reduce the release of inflammatory mediators, in order to reduce the inflammatory reaction; In order to improve the curative effect of antispasmodic drugs, it should cooperate with bronchospasmolytic substances. Therefore, the drug can be widely used in the clinical treatment of acute and chronic respiratory diseases with abnormal secretion of respiratory tract, especially in the expectorant treatment of chronic bronchitis, neonatal respiratory distress and adjuvant treatment of lung surgery. It has the advantages of low toxicity, exact curative effect, and can produce good synergistic effect with antibiotics. It is one of the most commonly used expectorant drugs.