Purpose To explore the feasibility of low radiation dose combined with lowdose contrast agent in thyroid CT enhanced scan and investigate the benefit of reducing radiation hazard and contrast agent damage to thyroid.Materials and Methods 120 patients assigned for thyroid enhanced CT scan were prospectively and randomly divided into four groups (each group was 30 patients).Group A:radiation dose 120 kV,180 mA,contrast agent dose 1.2 ml/kg;group B:radiation dose 120 kV,180 mA,contrast agent dose 1.0 ml/kg;group C:radiation dose 100 kV,100 mA,contrast agent dose 1.2 ml/kg;group D:radiation dose 100 kV,100 mA,contrast agent dose 1.0 ml/kg.CT values,background sign,background noise of thyroid were measured;signal to noise ratio (SNR) and contrast to noise ratio (CNR) were calculated;CT dose index of volume (CTDIvol),dose length product (DLP),and the effective dose (ED) were recorded and calculated.The image quality was evaluated and the data was statistically analyzed by two radiologists.Results CT values,background sign and background noise of thyroid,as well as CTDIvol,DLP,ED among four groups were statistical significant (P＜0.05);there was no significant difference in SNR,CNR and image quality scores among four groups (P＞0.05).Conclusion It is beneficial of reducing radiation hazard and side-effect of contrast agent from low radiation dose combined with low-dose contrast agent under the condition of ensuring diagnostic image quality.