Idioms are an important part of Teaching Chinese as a Second Language (TCSL), but current research on the meanings and grammatical functions of idioms is still quite weak. This study selected commonly used idioms in TCSL, extracted sentences containing these idioms from large-scale modern Chinese corpora, and manually annotated the meaning and grammatical functions of each idiom in these sentences. It then analyzed the characteristics of the idioms in TCSL and revealed the importance of meanings and grammatical functions in idiom teaching. This study further examined the problems of the idioms in textbooks and learner's dictionaries, proposed methods and principles for setting example sentences, and introduced how to carry out idiom teaching. This research not only provides theoretical and practical references for Chinese language teachers and learners, but also helps to promote the development of textbook editing, dictionary compilation, and idiom teaching.