Metaphor is an important cognitive tool.Image schema is the cognitive basis of metaphor,which plays an important role in the mapping of conceptual domains.Spatial metaphor has a special meaning for the formation of human concept,and it also appears as an image schema.The spatial prepositions in,on and at are commonly used in English,which most directly reflects the dynamic and static relationship of space.Based on the image schema theory and spatial metaphor,this paper explores the cognitive motivation and expansion way of the spatial metaphorical meaning of prepositions in,on and at.Image sch...