Abstract: Objective: Evaluated the influence of heart rate on image guality and delay time of dual-source computed tomography(DSCT)coronary Angiography.Methods: 310 patients were divided into five groups according to their heart rate(heart rate≤59 beat/bpm,heart rate≤69,heart rate≤79 beat/bpm,heart rate≤89 beat/bpm and heart rate≥90 beat/bpm),and image quality and delay time of coronary arteries was evaluated for all patients.Results: 99.9%(4 540/4 544)sements reached diagnostic.In group 2,3,4,5,image quality of coronary arteries had negative correlation with heart rate.In group 1,2,3,4,delay time also negative correlation with heart rate.Conclusion: Excellent coronary artery image could be obtained with dual-source CT without oral Betaloc preparation,but heart rate is also the most important factor that influences image quality and delay time.