Abstract: Metaphoric Competence(MC) is the key for second language learners to overcoming their L1 thinking habit and solving the problem of nonnative-like production in their target language. This paper was a comparative study of the effects of explicit/implicit metaphor instruction on the development of MC from the perspective of acquisition of polysemy by English majors. The findings indicated that there were similarities and differences in the effects of explicit/implicit metaphor instruction on the acquisition of polysemy and the development of MC. The similarity was that they were both able to improve learners' polysemy acquisition and MC, while their difference lay in the stronger influence of explicit metaphor instruction in promoting the effect of polysemy acquisition on the development of MC. The results showed that there existed a significant correlation between polysemy acquisition and MC. While explicit metaphor instruction had a stronger influence in a short term, SLA and MC developing was a process of mutual promotion in the long run.