The term metacognition was first put forward by American developmental psychologist John H. Flavell (1979). It literally means cognition about cognition, or more informally, thinking about thinking. Flavell defined metacognition as knowledge about cognition and control of cognition. Research has shown that metacognition plays a very important role in students' study and is the real factor that causes the differences of students' academic records. The relationship between students' metacognitive skills and their academic records is that the stronger their metacognitive skills are, the higher their academic records are. Students' metacognitive skills influence students' study in three phases: the phases of pre-study, study and post-study. This paper mainly talks about how to improve students' metacognitive skills in the three phases and make them do better in English studying. It can be done from three aspects: 1. Help students have a correct idea of learning. Students should learn to know about their study task and make a proper study plan before starting their study activities. 2. Train students to have the ability to choose proper learning strategies. Learning strategies is part of metacognition. Teachers should tell students their education principles and let students know the destination and the expected result of their teaching activities. Thus students could learn to choose proper learning strategies in their language study. 3. Improve students' ability of self-regulation in their language study. Self-regulation is the essence of metacognition. Teachers should be involved in specific teaching steps, know students' problems and puzzles and help students evaluate if they are approaching their aim.