Acquired long QT syndrome is a cardiac channelopathy, usually manifested by prolonged QT intervals in the electrocardiogram, which can lead to arrhythmias and an increased risk of sudden death. However, there is a diversity of drugs that target LQT syndrome. In this study, we simulated acquired LQT syndrome on a model of human ventricular cardiomyocytes and tested the therapeutic effects of potassium supplements and the L-type calcium blocker nifedipine on this basis. The results showed that the L-type calcium blocker and potassium ion supplementation could effectively shorten the action potential and QT interval of the ECG in cardiomyocytes and shorten the effective nonresponse period. Taken together, this study provides data to support the use of calcium channel blockers and potassium supplementation as a new treatment for LQTS.