Abstract: Factors influencing the deformation of a dry-dock slope were analyzed. They are soil mass strength, time of non-protection slope, gradient of slope, number of layout excavation, depth of layout excavation, excavation step, rainfall depth and load on slope top. Based on the above and the typical deformation data measured in-situ, an artificial neural network model of predicting the deformation of a dry- dock slope was proposed, and the prediction result is consistent with the measured in-situ result. In addition, the vigilance values for slope deformation for the expanding slope technology, the four judgement modes for slope deformation and their corresponding control measures were put forward.