A traditional assumption has been that written work in foreign language classes must be corrected carefully. If they were not corrected, errors would be deeply ingrained, and it would be difficult for learners to use the language correctly. Feedback has been viewed as a facilitator of learning and provides various kinds of information to the learner. In foreign language learning, this information consists primarily of modifications and upgrade their inter language grammar. Teachers" written feedback is a topic of continuing interest in foreign language teaching. But most experienced writing teachers know that responding to the students" writing can be the most frustrating, difficult and time consuming part of the job. Providing written feedback on student papers is the teachers‘ most crucial task. And it plays an important role in motivating and encouraging students. But in spite of corrections, teachers have found that students continue to repeat the same mistakes. Moreover the return of papers covered with red marks causes disappointment and discouragement on student"s faces. The teacher wonder if lerner"s errors should be corrected. If so, when should learner"s errors be corrected and which error should be corrected? How should learner"s errors be corrected? Who should correct learner"s errors? To this end, this paper will review the researches about these questions. And this paper will discuss and try to find the conclusion on these questions.