Angiotensin-converting enzyme inhibitors, like other antihypertensive drugs, also have adverse reactions, and although the incidence of adverse reactions is low, it is not absolutely safe. The most common clinical adverse reaction is dry cough, the incidence of up to 5%-20%, is irritating dry cough, may be related to the increase of certain substances in the pulmonary vasculature, causing irritation, cough response, patients often stop taking the drug because of cough. Hypotensive reactions occur in about 3% of patients, mostly in the first few days of treatment or when the dose of angiotensin-converting enzyme inhibitors is increased. This hypotensive response is especially likely to occur early in patients whose renin-angiotensin system (RAAS) responds significantly to stimulation. Hyperkalemia, angioneurotic edema, are also adverse reactions to this class of drugs. Both of these adverse reactions are more likely to occur after the use of angiotensin-converting enzyme inhibitors in those with impaired renal function, especially those with renal stenosis. In patients with bilateral renal artery stenosis or one kidney with renal artery stenosis, the use of angiotensin-converting enzyme inhibitors can induce acute renal failure. In patients with combined renal insufficiency but creatinine less than 3.0 mg/dL, angiotensin-converting enzyme inhibitors are the last option, but should be monitored by a physician. Angiotensin-converting enzyme inhibitors should be contraindicated in pregnant women. Studies have demonstrated that angiotensin-converting enzyme inhibitors can cross the placental barrier and cause fetal developmental disorders. Furthermore, clinical cases of neutropenia have been reported with angiotensin-converting enzyme inhibitors. Long-term use of angiotensin-converting enzyme inhibitors can also cause a decrease in blood zinc and lead to skin rashes, taste. The use of long-term angiotensin-converting enzyme inhibitors can also cause a decrease in blood zinc, resulting in rash, taste, smell, and hair loss. Zinc supplementation may improve symptoms. The above mentioned adverse reactions should be closely observed and monitored to detect and gradually reduce the dosage until discontinuation.