Cognitive Meaning of "for"

Based on the theories of image schema,metaphor,meaning chain and so on,the article analyzes the semantic extension of the preposition for,and attempts establish the meaning chain the various meanings of for from the perspective of cognitive linguistics.When trajector points landmark,the semantic extension of the preposition for is:from direction destination,spatial/temporal distance,hobbies or specialty and then from destination objective(gaining,representation,profit etc.),exchange,correspond to etc.successively.When landmark points trajector,for extends from direction reason.