This paper provides an overview of the theories on the organization and development of L1 mental lexicon and the representation mode of bilingual mental lexicon. It analyzes the structure and characteristics of Chinese EFL learners and their problems in English vocabulary acquisition. On the basis of this, it suggests that English vocabulary teaching should be adjusted to learners' various proficiency levels at different stages. Learners should pay attention to the mediating role of Chinese, cultivate their English thinking pattern, and strengthen the development of in-depth vocabulary knowledge.