llusion is the ultimate experience of garden mountain building. The scenery creates emotion, and the image is born from heart. Ancient literati often used paintings to convey their thoughts on mountains and forests as the beginning of garden creation. The mountain forest space created by mountains near lake in garden has aroused the thinking about fantasy space created by rockery. Based on the spatial scale of pavilion that is pleasing to eyes, this paper conducts a data comparison and analysis, combined with viewer's perception, and summarizes five conditions for creating a mountain space: elements that create the characteristics of mountain, the physical perception relationship between rockery and people,the scale control with reference object, the relationship between the mountain building in vertical space and the surrounding space of rockery. The purpose is to provide a new thinking angle for the rockery construction near lake, and to provide a theoretical reference for the inheritance and innovation of current garden orogenic techniques.