Obiective To obvserve the influence of hemodialysis on Q-Td in the patient of chronic renal failure. Methods We have obvserved 63 cases the patients of chronic renal failure who have treated by maintenance hemodialysis during 2000～2001 year, we checked electrocar diogram electrocardiograph on pre-dialysis,1 hours,2 hours and post-dialysis and estimated Q-Td time or Q-Tcd. Results Q-Td time (62.1±16.9) and Q-Tcd (68.3±16.9) all of chronic renal failure the patient is elongation than normal person; post-dailysis Q-Td time and Q-Tcd is shorter than pre-dialysis. Conclusion Chronic renal failure patient occurrence probability of malignancy arrhythmia and sudden death due to heart failure to increase, but it can reduce risking by law and high efficiency hemodailysis, rise hemodailysis survival rate.