Abstract: Objective: To investigate the variations in radiation dose during dual-source computed tomography (CT) high pitch spiral scanning with and without electrocardiogram (ECG) gating. Materials and Methods: A phantom was scanned using dual-source CT. Scanning was performed with ECG gating and non-ECG gating techniques under automatic exposure control and non-automatic exposure control, using the same reference voltage of 100 kV and reference amperages (ECG gating group 400, 480, and 560 mAs/rot; non-ECG gating group 125, 150, and 175 mAs). The variations in radiation dose and image noise were measured. Results: Under automatic exposure control, the radiation doses of the ECG gating group (400, 480, and 560mAs/rot) and the non-ECG gating group (125, 150, and 175mAs) were not equal; fully automatic tube voltage modulation, t=−6.247, P < 0.05; semi-automatic: t=−6.247, P < 0.05; and closed: t=−9.475, P < 0.05. There were also differences in the image noise. Under non-automatic exposure control, the radiation doses of the ECG gating group (400, 480, and 560mAs/rot) and the non-ECG gating group (125, 150, and 175mAs) were equal (t=1.250, P=0.338), and the image noise was equal. Conclusion: Under automatic exposure control, the radiation doses and image noise of ECG gating and non-ECG gating were not equal but under non-automatic exposure control, they were equal.