Based on the analytic framework for examining the language use and functions of teacher feedback， this paper explores L2 writing teacher written feedback practices by looking at the use of L1 and L2 in written feedback and the speech functions of feedback in L1 and L2． The study finds that EFL teachers tend to use a certain amount of Chinese ( a quarter or so) to give written feedback to L2 essays and the findings indicate four fundamental functions of speech ( referential， directive， expressive and metalinguistic) in teacher written feedback， with referential function being predominant in their feedback practices． It also reveals a significant difference between functions of feedback in L1 and those in L2． Compared with L2 feedback， L1 feedback focuses on the content of students' writing in referential function， expressive and metalinguistic functions， which can stimulate dialogic interaction and negotiation of meaning between teachers and students． Implications and suggestions regarding the use of L1 and how to improve the interactive nature of teacher written feedback are proposed