Abstract： Objectives To investigate the image quality,influencing factors and radiation doses of prospectively ECG-triggered spiral acquisition mode (Flash spiral mode)coronary computed tomography angiography (CCTA) using high-pitch dual-source CT in patients with different heart rates.Methods One hundred and thirty-four consecutive patients with mean heart rate (HR) ＞ 65 beats per minute (bpm) and ≤ 100 bpm were included in this study as group A using Flash spiral mode setting at 20％ -30％ of the R-R interval and 134 consecutive patients with mean HR ≤65 bpm were enrolled as group B using Flash spiral scan mode at 55％ of the R-R interval; 134 consecutive patients with mean HR ＞ 65 and≤100 bpm using spiral scan mode were included as group C. The image quality scores, effective radiation dose and influencing factors of image quality in three groups were assessed. All statistical analyses were performed using SPSS.Results (1)The non-diagnostic coronary artery segments in group A (28/1842,1.52％) were more than in group B (8/1819,0.44％ ) ( x2 =10.97,P =0.001 ) and there was no significant difference between group A and group C (32/1838,1.74％) ( x2 =0.280,P =0.345).The number of patients with non-diagnostic coronary segments in group A( 10/134,7.5 ％ )was more than in group B (2/134,1.5 ％,x2 =5.52,P =0.018 ),while there was no significant difference between group A and group C (9/134,6.7％,x2 =0.057,P =0.812).(2)The average heart rate variability (HRV) of patients with different image scores in the three groups wcrc significantly different. In group A,the HRV of score 1,2 and 3 were (2.29 ± 1.06),(5.17 ± 1.37),(8.88 ± 1.53) bpm,respectively (F =170.402,P =0.001 ).In group B were (2.26±1.01),(5.97 ±1.82),(12.00 ±9.64) bpm,respectively (F=95.843,P=0.001).In group C were (2.61 ±1.85),(7.90 ±3.97),(11.22 ±5.62) bpm,respectively (F=68.629,P=0.001 ). (3) The average effective radiation doses in groups A and B were significant lower than in group C [ A group was 1.04 ± 0.16,B group was 1.03 ± 0.16 and C group was 7.05 ± 1.05,t =65.5 ( A vs C),P ＜0.01 ( A vs C) ].Conclusions Flash spiral mode of high-pitch dual-source provides high image quality with significant reduction of radiation exposure in patients with HR ≤ 65 bpm. Patients with heart rates ＞65 bpm and ≤100 bpm without cardiac arrhythmia can perform CCTA using Flash spiral mode with image acquisition time setting at 20％-30％ of the R-R interval.