A Valediction: Forbidding Mourning is one of the masterpieces of the metaphysical poet, John Donne. The poem was written when the poet was sent to France on business and had to be separated from his wife, who was about to give birth. The poem uses a lot of metaphors to describe the pure love between the poet and his wife, and explains that distance can separate them. Influenced by the environment of the time, Donne used metaphors in his poems involving astrology, refining technology, and geometry. Donne used these seemingly unrelated elements of love to describe the feelings between his wife and himself, which formed his own unique style, and his love poems have been widely praised by later generations. This thesis uses the mapping theory in cognitive linguistics to further analyze the main metaphors mentioned in the poem, in order to make readers have a clearer and deeper understanding of metaphors and the poem.