This study reported the capillary imbibition of ethanol in a cement paste traced by X-ray computed tomography (X-CT) enhanced by CsCl. Results show that CsCl can promote the contrast of X-CT images due to the significant X-ray absorption of Cs. The grey value distributions of horizontal section images were calculated to identify the penetration fronts of the CsCl-ethanol solution in the cement paste. The relationship between imbibition height and time follows the Lucas-Washburn equation. The method of enhancing X-ray sorption by CsCl paves a wide path to in situ monitor liquid imbibition in porous materials for assessing their microstructures and properties.