Based on the conceptual metaphor theory, this paper focuses on applying the metaphor-enriched medical English supplement to the College English class to facilitate the metaphoric competence of students and the learning of Medical English, aiming to facilitate college students to migrate smoothly from English for General Purposes to English for Specific Purposes (Medical English). One unit in the textbook was selected to be analyzed from the prospective of metaphor and the related medical knowledge was supplemented. A test was conducted before and after the implementation as the pre-test and the post-test. The collected data were analyzed via NVivo 11 and SPSS 22.0. The result shows that metaphor-enriched medical English supplement did improve students' metaphoric competence and enlarge their medical knowledge. On one hand, the metaphorical cognitive mechanism is consistent with the process of English learning which is an interaction between the old language knowledge and the new one. On the other hand, it is an effective method to understand medical words by metaphoric thinking, that is, to perceive as many morphemes as possible from the existing Medical English terms and remember these terms in relation to their forms.