Abstract: The charact eristic of groundwater flow changed appa rently under high-temperature situations.The normal Darcy's law is not admissible at high-temperature situations.The reason is that the existence of tempera ture-gradient has direct and indirect effect on the flow of water body.In this paper,the theory of thermodynamics is used to solve the macro-balance equati on of momentum of fluid phase.Then the modified equation of motion for high-tem perature situation is presented.The modified equation can be used in practical problems,such as the usage of geothermal resources in China,the transport of groundwater with high-temperature found recently in the world.