Sudden tachycardia in hyperthyroidism requires vigilance for thyroid crisis. Thyroid crisis is a syndrome of acute exacerbation of thyrotoxicosis, which is mainly related to the large amount of thyroid hormones into the circulation, and can be treated by targeting the causative factors, medication, and other supportive treatments. 1. Treatment for triggers: common triggers include infection, trauma, mental stimulation, etc. Patients can be given treatment for triggers, such as active anti-infection treatment. 2. Drug therapy: anti-thyroid drugs can be given to inhibit thyroid hormone synthesis and inhibit the conversion of T4 to T3 in peripheral tissues; β-blockers can be given to block the stimulating effect of thyroid hormone on the heart; iodine can also be used to inhibit the release of thyroid hormone. 3. Other supportive treatments: when conventional treatment is not satisfactory, peritoneal dialysis, hemodialysis or plasma exchange can be used to reduce the concentration of thyroid hormone. For patients with hyperthyroidism and sudden tachycardia, it is recommended to consult a doctor in time and follow the doctor’s instructions for standardized treatment.