In the present study, the radiation dose and image quality between two techniques, namely; automatic tube current modulation (ATCM) and fixed tube current (FTC), in computed tomography (CT) of multiphasic examination of the liver, were evaluated. For this objective, fifty liver CT patients examined were investigated by arterial, portal, venous, and equilibrium measures following scans of hepatic circulatory phases. All stages, except for tube current, a portal, and a venous phase, have been carried out by the FTC, ATCM and correlated with their dosage and image quality, with similar scanning and reconstruction parameters. In these techniques, the CT unit automatically displays , both the radiation dose measurements and the dose index volume (CTDIvol), simultaneously. Also, for quality insurance, the images obtained were quantitatively evaluated by the contrast noise ratio (CNR). The results showed that the averaged of CTDIvol was 26.07 mGy in FTC, and 13.71 mGy in ATCM. As compared with the FTC technique, CTDIvol was reduced by using the ATCM technique. The average value of CNR were(28.93, 29.98) HU in FTC and ATCM, respectively.