This paper discusses research on the quality of teaching Chinese as a foreign language. Rather than to use a collection of data, the paper begins with the fundamental meanings of jing1 guo4, tong1 guo4, tou4 guo4, and discusses their differences to arrive at some useful ideas for teaching. The structure of the papers is as follows. It first examines the basic meanings of the three phrases based on their dictionary definitions. It then compares their meanings and analyzes their differences. Finally, it reviews textbooks that teach these three lexical items, and offers some suggestions on how to teach them.