To study the potential role of dynamic electrocardiogram(DEG) in silent myocardial ischemia (SMI) patients, we measured the extension of ischemia and heart rate variation-time-domain analysis in 148 patients with SMI and 30 healthy controls by DEG and followed up all patients for 1.5 years. The results were that the extension of myocardial ischemia (the extension of ST segment depression, episodes of SMI attack, and the total ischemia time), the incidence rate of ventricular premature heat increased gradually and the difference of heart rate. Heart rate variant hinder(HRVI), and SDNN decreased gradually in SMI I, III, II types. And the extension of ischemia had positive correlation with the lowest heart rate and the incidence rate of ventricular premature beat, while negative correlation with HRVI and SDNN, indicating that the impairment of cardial autonomic nerves is associated with the extension of ischemia. Also, we found that 23 patients out of 148 patients with SMI died and the levels of HRVI and SDNN of the patients who died were lower than that of the survivals. We conclude that the heart rate variability can serve as a prognosis index of SMI.