Abstract： Objective To evaluate the value of iterative modal reconstruction (IMR) for reducing radiation dose and controlling image quality in cardiac CT. Methods Ten pigs were included. All pigs were scanned on a 256?slice prospectively ECG?gated cardiac CT utilizing routine dose (group A) and tube current reduced by 30%(group B), 50%(group C) and 70%(group D), respectively. Filtered back projection (FBP), hybrid iterative reconstruction (iDose4) and IMR were used for all data, respectively. Image noise and contrast?to?noise ratio (CNR) of ascending aortic root were measured, while overall image quality and coronary artery image quality was rated (five point scale). All results reconstructed by FBP, iDose 4 and IMR were compared. Objective measurements were compared with one?way analysis of variance, and subjective assessments were compared with Kruskal?Wallis H test andχ2 test. Results Compared with that of FBP and&nbsp;iDose4, image noise of IMR was(15.1 ± 6.1),(18.8 ± 5.5),(22.1 ± 4.8)and(33.0 ± 4.0)HU, respectively in group A, B, C and D with significant reduction (F=82.77, 90.71, 96.59, 95.51 respectively, all P<0.01). Using IMR, groups A, B, C, D had higher CNR (42.0±11.1, 37.2±10.4, 31.4±8.7, 23.7±7.0;F=50.65, 53.55, 76.60, 57.36, all P<0.01) and overall image quality (5.0 ± 0.0, 4.8 ± 0.4, 4.6 ± 0.5, 4.5 ± 0.5;H=20.96, 15.63, 18.66, 23.56, all P<0.01) than FBP and iDose4. Using IMR, group A (100%, 40/40) and group B (100%, 40/40) had no significant difference (P>0.05) in the diagnosis rates of proximal coronary arteries compared with that using FBP and iDose4, while group C (100%, 40/40) and group D(92%, 37/40) had significantly increased diagnosis rates (χ2=20.05, 45.72, both P<0.01). The diagnosis rates of distal coronary arteries of IMR reconstruction which were 100%(50/50), 98%(49/50), 90%(45/50), 78%(39/50), respectively in groups A, B, C, D had significant increase compared with that of FBP and iDose4 reconstruction (χ2=7.39, 16.75, 34.62, 81.33, all P<0.05). Conclusions IMR can significantly reduce image noise, improve CNR and image quality compared with iDose4. Application of IMR can reduce radiation dose but without compromising image quality.