Long Q-T syndrome (LQTS) is an ion channel disease of the heart featuring single gene inheritance. It is characterized by prolonged QT interval, abnormal T wave, torsade de points (TdP) on electrocardiogram, with recurrent syncope, convulsion and even sudden death. Although the overall prevalence of LQTS is not high, the disease has attracted attention of cardiologists for its high incidence of sudden cardiac death. The compilation of this guideline has referred to the consensus of basic and clinical research, guidelines of other countries, and summarized the clinical manifestations, molecular basis, diagnostic criteria, treatment and prognosis, and genetic counseling of LQTS, with an aim to standardize its clinical diagnosis and treatment.