Accurate and efficient gas-liquid two-phase flow simulation is of great significance to energy, chemical industry, aerospace, environment and other fields. Although the Euler-Lagrange method can accurately simulate the motion of droplets, its computational complexity increases significantly with the number of droplets, thus it’s difficult to be applied to practical applications. Therefore, based on the explanation of the physical mechanism of the droplet movement in the steam-water separation device, combined with the Euler-Lagrange model, the Euler grid approximation model is established, which can simultaneously calculate the information of the whole droplet field and reduce the amount of computation while maintaining accuracy. In this model, the Lagrange description of droplet motion is approximated by Euler grid approximation method, and the real droplet motion is approximated as the motions of droplets along the grid nodes, so that the line between nodes is used to simulate the flow line. This paper gives the physical mechanism explanation and mathematical expression of the Euler grid approximation model to obtain the velocity, density, rotation under the gravity field, and the accuracy of the method increases with the refinement of the grid. The Euler grid approximation method can be applied to droplet motion subject to body force, as well as multi-droplet motion.