Thermal ablation by radio frequency (RF) is widely used in the minimally invasive treatment of focal tumors. Since different ablation devices often have different thermal properties, it is vital to create a standard to help physicians compare devices and train new physicians. Currently, the usage of existing approaches (such as MRI thermometry and tissue phantoms) is often limited by the cost and inability to collect quantifiable performance data. In this study, a computed tomography (CT) imageable phantom was developed to provide quantitative assessments of thermal ablations. The experiments proved that there are linear correlations between the impedance and salt concentration, and between the size of the ablation zone and generator power. However, there is no relationship between the size of the ablation zone and salt concentration. The fabricated phantom can simulate tissue ablation and provide valuable information for both training and device characterization.