As an old saying goes that“once you open mouth, you are decided”. Thus, there is no doubt about the fact that English pronunciation is of great importance, especially for English teachers whose pronunciation exerts far-reaching and direct influences on that of students. Some of College English teachers, however, have poor pronunciation; most of them cannot distinguish/n/ from /l/. Therefore, it is of huge practical value to commit to the research on the mistakes made by College English teachers in pronunciation of /n/ &/l/ and analyze the underlying causes in the hope of helping teachers to improve their poor pronunciation. As an old saying goes that “once you open mouth, you are decided ”. Thus, there is no doubt about the fact that English pronunciation is of great importance, especially for English teaching whose pronunciation exerts far-reaching and direct influences on that of students; Some of College English teachers, however, have poor pronunciation; most of them can not distinguish / n / from / l /. Therefore, it is of huge practical value to commit to the research on the mistakes made by College English teachers in pronunciation of / n / & / l / and analyze the underlying causes in the hope of helping teachers to improve their poor pronunciation.