Formulaic language plays a vital role in people's oral expression and writing ability. In the process of writing, formulaic language occupies a very large proportion. This paper conducts an experiment to prove: 1. Formulaic language can reduce the language processing time, thus shorten the writing time and increase the fluency of writing; 2. Formulaic language is conducive to expanding the students' vocabulary and improving the authenticity and vividness of their writing; 3. Formulaic language is conducive to enhancing the coherence and logic of the writing. In short, formulaic language directly affects the students' writing ability. Therefore, teachers should promote the students' formulaic language knowledge in daily teaching, help students acquire formulaic language and improve their second language acquisition.