Abstract: Rainfall landslide and debris flow warning must be advanced. Through analysis and summary of previous research results, the author divides the early warning of rainfall landslide and debris flow into two major types, namely, space warning and time warning. The goal of space early warning is to predict the occurrence trend of landslide and debris flow disasters in macro areas and divide the dangerous areas in different times. The goal of time warning is to forecast the possible time stage of typical landslide and debris flow. Based on the principle of early warning classification, this paper establishes a technical and methodological system of two types of disaster early warning, which constitutes the principle and system structure of early warning for landslide and debris flow in rainfall.