Through investigation and analysis,the importance of environmental regionalization for natural hazard prevention and treatment has been revealed.Based on the work,principles for highway flood hazard environmental regionalization,such as regional differentiation,similarity,integration of comprehensive analysis,dominant factors,and practicability,are put forward.According to the principles,the index system for highway flood hazard environmental regionalization in Chongqing City is studied systematically.Based on the causes of highway flood hazard,a two stage index system is established by using Delfei method.The weight of each indicator is determined in the light of its relation with highway flood hazard by using analytic hierarchy process.The classification system of the secondary indicator including 5 grades is set up based on the outcome of in-situ investigation and analysis of historical data.The value of the secondary indicator for each grade is also determined by using Delfei method and thus the methodology for calculating synthetically the value of highway flood hazard environmental regionalization is formed.The classification and corresponding criterion for highway flood hazard environmental regionalization are brought forward subsequently,which provide a basis for environmental regionalization work.