Atmospheric advection equations are generally used for numerical forecast on the grid field. It is rarely applied to the extrapolation of discrete elements. The extrapolation of model discrete elements not only makes the data filling in time more meaningful, but also lays the foundation for forecasting elements of a site. The model, based on discrete site characteristics, reforms the advection equation to get the wind speed of sites and gradient eigenvectors. The Gauss expression of the likelihood probability of the advection terms is fitted by the frequency statistics, and the numerical solution of the newstyle advection equation is calculated. Through the singlepoint and multipoint actual tests, the specific application characteristics of the model are obtained, and a real data filling case is given. The results indicate that it worked well. The model is compact, efficient and easy to use, has good universality. As a general mathematical model, it provides a new idea for the element prediction at discrete points.