Objective To analyze the distribution and causes of QT interval prolongation in hospitalized patients. Methods A total of 61 patients with QT interval prolongation (corrected QT interval ≥ 500 ms) diagnosed by electrocardiogram in The First Affiliated Hospital of Naval Medical University (Second Military Medical University) from Jan. 30, 2019 to Jul. 27, 2022 were enrolled. The baseline characteristics of patients were collected, and the departments of the patients and the causes of QT interval prolongation were analyzed. Results Coronary heart disease, hypertension, diabetes mellitus, and tumor accounted for 50.8% (31/61), 45.9% (28/61), 23.0% (14/61), and 8.2% (5/61) of hospitalized patients with QT interval prolongation, respectively. The inpatient departments of patients with QT interval prolongation were mainly Department of Emergency (45.9%, 28/61) and Department of Cardiovasology (31.1%, 19/61). The causes of QT interval prolongation were drugs (44.3%, 27/61), coronary heart disease (26.2%, 16/61), and electrolyte disturbances (24.6%, 15/61). The common drugs that prolonged QT interval were classⅢ antiarrhythmic drugs, antibiotics (macrolides and quinolones), and 5-hydroxytryptamine receptor antagonists. Among the 61 patients, 3 (4.9%) cases had torsade de pointes and 6 (9.8%) died during hospitalization. Conclusion In hospitalized patients, QT interval prolongation is more common in Department of Emergency and Department of Cardiovasology. Most of them are acquired QT interval prolongation, and the common causes are drugs, coronary heart disease, and electrolyte disturbances.