Objective To explore a quality assurance testing method for gemstone spectral imaging (GSI)computed tomography. Methods A phantom prototype made of 9 bottles of pure water mixed with Iopamidol (300 mg I/mL)at different Iodine concentra-tions was scanned using the GSI mode under a routine head protocol on a GE Discovery CT750 HD scanner.Then the images were post-processed on a GE AW4.6 workstation.Results Based on the effective atomic number histogram,water & Iodine scatterplot and spectral HU curve,the Iodine solution concentrations of the phantom were not only differentiated but quantified.Conclusion It is feasible to test the material decomposition capability of GSI with the phantom prototype.