By looking up pixels of image sequence as moving gas molecules, a novel concept, image temperature, has been proposed to describe the natural property of the image motion. The idea comes from the reveal of Maxwell-Boltaman Distribution Law in gas dynamic theories. Further, we develop another concept of energy flow corresponding to optical flow. Based on the concepts and the method of optical flow analysis, we developed the method of the Energy Flow Equation (EFE) to estimate image motion. Experiment indicates better performance of the proposed EFE scheme with significantly reduced false motion estimates than the traditional Optical Flow Equation does.