Expectorants are mainly used for patients with cough with phlegm, and clinically one or several expectorants are often chosen for combined use according to the sputum properties. When the cough is so severe that it affects rest and work, the appropriate amount of cough suppressant can be added to form a compound (such as compound licorice agent, etc.). The former, such as ammonium chloride, potassium iodide, guaiac glycerine ether, orris, Yuanzhi, etc., can stimulate the gastric mucosa after oral administration, causing slight nausea and reflexively promoting the secretion of respiratory glands to dilute sputum and make it easy to cough up; the latter are some volatile substances, such as eucalyptus oil and tincture of benzoin, etc., added to boiling water, whose vapor can stimulate the mucous membrane of the respiratory tract and increase the secretion of glands. The latter is some volatile substances, such as eucalyptus oil, benzoin tincture, etc. added to boiling water, and its vapor can stimulate respiratory mucous membrane, increase gland secretion, make sputum dilute and easy to cough up. 2.Mucolytic agents such as acetylcysteine can decompose the viscous components of sputum such as mucopolysaccharide and mucin, so that the sputum can be liquefied and the viscosity can be reduced and coughed out easily. 3.Mucus regulators such as bromoxyn (Biocortisone), amiloride (Mucosolvan), etc., mainly act on mucus-secreting cells of trachea and bronchus to promote them to secrete less viscous secretions, so that sputum can be thinned from sticky to thin and easily coughed out. 4.Mucus promoting agent Acts on mucus cilia clearance system to promote sputum discharge, such as β2 agonist. Some expectorants have several effects mentioned above, such as standard myrtle oil, etc. Long-term application of expectorants in patients with chronic cough and sputum in chronic obstructive pulmonary disease can keep the airway open, prevent acute attacks, reduce the incidence and degree of acute attacks, reduce the need for antibiotics due to deterioration, and alleviate the health disorders caused by cough and sputum.