High concentration barium sulfate has been developed and used in mass screening for gastric cancer. However, high concentration barium sulfate flows out from the stomach faster than moderate concentration one, which often interferes with diagnosis. The speed of flow is seemed to depend on the viscosity of barium sulfate. Previously, the authors reported viscosity changes of high concentration barium sulfate with pH and temperature changes. In this study, it is examined that the viscosity of barium sulfate also changes with artificial gastric juice volume. The results indicate that the viscosity of high concentration barium sulfate is more stable than that of moderate concentration one and the image of gastric phantom with high concentration barium sulfate is evaluated to be better than that with moderate concentration one. The study on characteristics of barium sulfate may improve radiography technology in mass screening for gastric cancer.