In the statistical process of ground flash density, the grids need to be divided in kilometer, and then the data of lightning flushes falling in the grids need be counted. The concept of dimension reduction is used to compute the ground flash density for the first time. During the contour drawing, all the data are involved without missing data. The manual statistical method is described, and the statistical method of dimension reduction is achieved by using the Java language at the same time, which provides a friendly interactive interface. The application proved that the statistical method has a very good practicability.