This study discussed the relationship between fluid viscosity and swallowing flow. We simulated numerically the liquid bolus flow near the epiglottis using digitized 3D bolus geometry, which was constructed from coronal and sagittal video fluoroscopic examination. The temporal changes in the 3D bolus geometries were numerically analyzed as fluid flow. We discussed the movements and the inside velocity distributions of the bolus. The influence of the bolus viscosity on the bolus flow was also discussed.