Researchers have explored second language (L2) teachers' knowledge focusing not only on their prior language learning experience, previous L2 teacher education, and teaching practices, but also on specific curricular areas, such as teaching L2 grammar, teaching L2 reading, and teaching L2 writing. This line of research has contributed to L2 teacher education, particularly how to develop an effective knowledge base for teacher candidates. This dissertation was conducted to investigate English as a foreign language (EFL) teachers' knowledge of vocabulary instruction. Specifically, employing three qualitative techniques for data collection (i.e., interviews, classroom observations, and stimulated recall), the study examined seven Chinese EFL university teachers'knowledge of vocabulary instruction from four dimensions: their beliefs about vocabulary learning, their understandings about vocabulary teaching, the relationship between their knowledge of vocabulary instruction and vocabulary teaching practices, and the sources of their knowledge about vocabulary instruction. The findings of the study indicate that Chinese EFL teachers have well-developed content knowledge of EFL vocabulary. They also have well-established belief systems about how to learn and teach vocabulary. Moreover, their beliefs about vocabulary teaching tend to be consistent with their vocabulary teaching practices though some inconsistencies have been identified as well. It was also found that Chinese EFL teachers¡¯ knowledge of vocabulary instruction is derived from a variety of sources, of which formal EFL education and teaching practices are considered as the two most influential. EFL teachers' individual differences were also identified to impact their beliefs about vocabulary instruction. This dissertation has at least three potential contributions. As one of the first attempts to investigate teacher knowledge of vocabulary instruction in the field of L2 teacher education, this research expands studies on L2 teachers' knowledge base. It also provides information about L2 teachers' knowledge in one less studied context, i.e., Chinese EFL vocabulary teaching. Finally, the use of observations, interviews, and stimulated recall to collect data in this study serves as an impetus for enriching techniques to examine Chinese EFL teacher knowledge.