Abstract: The development degree and homogenity of fault structures in a rock mass are the significant factors affecting structure types of the rock mass, rock mass quality, stability and comprehensive utilization of the engineering rock mass. Thus,it is important to estimate quantitatively the development degree and grade fault structures in the engineering rock mass. The permanent shiplock slope engineering in the Three Gorges Project is taken as an example, the methods to evaluate the development degree of fault structures are discussed systematically in this paper. A grade scale and the principles to decide indices are put forward. Results show that the comprehensive fuzzy evaluation and the artificial neural network are feasible to estimate the development degree of fault structures in rockmass based on regularity and patterns of the fault structure.