Abstrcat Reservoir area of Fengjie County's new city construction in Three Gorges is greatly changing Lijia Gully's engeering geological environment at midstream and downstream. The debris flow will threaten the construction of the new city and security of local people's property directly. The thesis proceeds from the point of geological project, the formation conditions(lithologic character, structure condition, geomorphic condition, meteorological condition, vegetative cover and human engineering activities), essential features(features of forming areas and circulating area) are systematically studied in detail. The calamity and development trend are predicted, and rational suggestions are proposed