The mountain equivalent rainfall concepts and calculation methods are proposed, borrowing from the national rainstorm warning standards for the debris flow early warning, so that they can be used as a uniform standard for both rainstorms and debris flow warning. The functions of the mountain equivalent rainfall ultimately are based on three facts: (1) the national standard is two times as much as the western mountain standard for the same storm warning; (2) most of the debris flow disasters occur around the altitude of 1300 m; and (3) the relationships between altitude and disaster can be described with Gaussian distribution, which is used widely as the formula by meteorological and land planning departments to determine the potential effect of pre precipitation accumulated rainfall on debris flow. The mountain equivalent rainfall formula can achieve the desired effect in the sampling simulation and evaluation tests and various environments, such as plains, mountains, and the plateau at different altitudes. The mountain equivalent rainfall formula has been used in the automatic releasing on a web site for debris flow early warning and analysis. Its application results need to be further verified in practice.