Micro-lesson attracts students' interest in watching with its short and pithy content, and teachers should make use of students' interest to make micro-video achieve the maximum educational effect. After the micro-video is made, it is aimed at the majority of students, but we can't guarantee that all students will have the perseverance to watch consciously, and demand determines action. So when do students need to watch the micro-video made by the teacher? The survey shows that students will watch micro-videos made by teachers when they preview their knowledge, or when they encounter difficulties in classroom study that day, or when they encounter difficulties in completing their homework at home.