Heart rate slowing drugs are mainly used for the treatment of sinus tachycardia, supraventricular tachycardia, rapid atrial fibrillation and other tachyarrhythmias, and the commonly used drugs include beta receptor antagonists, calcium channel blockers, digitalis drugs and so on. Each drug has a different mechanism of action, different indications, and different routes of administration, and there are various adverse reactions and side effects in the process of use, so it is impossible to say absolutely which heart rate slowing drug is safe. The safest drugs to lower heart rate are those that have good indications, pay attention to monitoring and follow-up, and reduce the occurrence of adverse reactions. beta-receptor antagonists such as betalactam are commonly used to treat sinus tachycardia, which may cause sinus bradycardia and aggravate heart failure. Calcium channel blockers such as verapamil are often used for the treatment of tachycardia, which may cause atrioventricular block and cardiac arrest. It is important to clarify the diagnosis before using the drug and pay attention to the observation and follow-up.