Flash flood is a typical natural disaster in the Northwest mountainous region of Vietnam, however forecasting is difficult due to its complexity and the impacts of global climate change. The purpose of this study is to identify areas at high risk of flash floods based on the actual characteristics of the study area using a multi criteria decision model. Slope, land use, soil texture, and rainfall are selected and weighted criteria corresponding to its impact on flash flood potential in the study area. The AHP (Analytic Hierarchy Process) method is a multi–criteria analysis method used to determine the comparative correlation between the criteria, thereby building the flash flood risk zoning map. Accordingly, the study area is classified into five levels: very low risk area, low risk area, medium risk area, high risk area, and very high risk area. The research results have shown that flash floods have a very high risk of forming in the north and northeast of the study area with above 15 % of the total area, of which the main distribution is in Lai Chau and northeast of Son La province. The research results are reliable documents for natural disaster prevention and environmental resource management in the Northwest.