Assessment literacy (AL) has emerged as an important research field during the past decade, yet it remains a great challenge for secondary school EFL teachers in China to appropriately enact their assessment literacy. Due attention needs to be paid to research upon teachers' conceptions of assessment (CoA) and assessment practice. Based upon a semester's observation of the English classes in a secondary school in China, weekly meetings on English teaching and research, a focus group interview, individual interviews, documents such as the participants' lesson plans and reflective journals, this qualitative study aims at exploring: (1) what are the conceptions of assessment of the participating secondary EFL teachers? (2) what is the teachers' assessment literacy in practice (TALiP)? (3) How could their assessment literacy be enhanced? Self-reported findings show that the EFL teachers have a wide scope of conceptions of assessment and individual variations in their assessment practices. The former range from knowledge of assessment purposes and criteria to regarding assessment as learning (AaL), and the latter from giving instant feedback of nodding or simple comments to practicing assessment for learning (AfL) in classroom teaching. Findings from observation also reveal that when tempting AaL, the participants could generally achieve AfL to some extent. Implications for further teacher professional development are discussed concerning how to enhance assessment literacy mentoring in internship and in-service training.