Abstract: The deformation of a side slope depends on several factors,such as geological condition,rainfall and underground water.However,the relationships between these factors and deformation can not be surely regarded as determinate and quantitative.In this paper the fuzzy relationships between different factors and displacement as well as the fuzzy approximate inference of displacement are analyzed,then based on this the application of fuzzy artifical neural network to deformation predication is introduced and demonstrated by a practical example of a side slope deformation monitoring.