Bio-heat transfer in the tongue body is studied combining the mechanism of tongue inspection in Traditional Chinese Medicine. Parameters such as the temperature of lingual surface, the blood perfusion of the dog's tongue and so on are measured and the influences of the blood perfusion, the arterial blood temperature, the arterial cross-sectional areas and positions on the temperature distribution in the cross-sections are studied. Then the two-dimensional temperature fields in different cross-sections are numerically solved by the finite element method (FEM). The results show that the vascular cross-sectional areas vary with the elasticity change of the vessel walls resulting from the variation of the blood perfusion. And the temperature distribution in the cross-section mainly depends on the arterial cross-sectional areas and positions. The results can help to analyze the bio-heat transfer characteristic of the tongue. According to this method, the sectional temperature fields in whatever place of the tongue can be calculated under different blood perfusion and on the condition that the influence of the venous blood temperature on the temperature field of the tongue is considered. We can further probe into the relationship between the temperature fields of the lingual surface and that of cross-sections. This can provide the foundation for further investigation into the bio-heat transfer mechanism and the calculation on three-dimensional temperature fields of the tongue.