Effective English writing has long been a challenge in English language teaching. With the development of cognitive psychology, metacognition has drawn more and more researchers' attention and provides a new perspective for EFL writing. Metacognitive theory mainly includes metacognitive knowledge and metacognitive strategy. Among all the learning strategies, metacognitive strategy is a higher-order executive skill which includes planning, monitoring and evaluating. Once learners have a good command of metacognitive strategy, they will become more independent and autonomous and will be more capable of planning, monitoring and evaluating their learning process and thus become efficient learners. However, the study of metacognitive strategies-based writing instruction for vocational college students has been neglected for the past years. The author, therefore, carried out an empirical study to investigate the effect of metacognitive strategy training on students' writing performance in the hope of finding an optimal teaching approach for English teachers of vocational colleges. This teaching approach really embodies the teaching idea "student-centered" and is targeted to foster students' metacognitive strategy, monitoring and evaluating abilities in English writing.