Abstract: Comprehensively applying DELPHI, AHP (Analytical Hierarchy Process), the most optimal model in synthesis evaluation, broad quantitative method and the theorem of grey system in thie paper,the assessment factors system of urban ivestment environment is discussed. Methods are improved to calculate weighed value and quantitative factors. The model of synthesis evalution in urban investment environment is established, synthesis evalu-tion supporting system for urban investment environment is developed and applied to evalu-ating for fifty-nine cities in Sichuan, Yunnan, Guizhou, Guanxi, and Hainan, the effect is very satisfactory.