Abstract: As the basic cognitive tools, metaphor and metonymy serve as the important constructive and interpretive mechanisms of multimodal discourses. The political cartoon is an important genre of multi-metaphor and multi-metonymy. This paper found that metaphor and metonymy display complex interaction. They may play the role independently or interact in the source domain, target domain or the mapping process. Metaphor mainly reveals the evaluative, expressive and emotive functions while metonymy functions as the bridge between the pictorial world and the real world, yielding distinct genre features.