Abstract: Polysemy, a linguistic phenomenon which reflects the cognitive ways that human beings recognize the world, makes up a vital part in English vocabulary teaching. Metaphor and metonymy are the motivation behind polysemy and polysemy is realized through an imaginary network of metaphor and metonymy. For English teachers, in order to conduct Polysemyteaching efficiently, the cognitive motivation of polysemy, the imaginary network of polysemy and the cognitive mechanism of polysemy should be taken into consideration.