The study of learning strategies is an important part in the field of second language acquisition，which is recognized that some language learners learn a second language more effectively and successfully than others.

1 The definition of learning strategies

Chamot and O’Malley （1987） believe that learning strategies are the skills，methods and conscious behaviors that learners use them to help with learning.Rubin （1987） suggests that learning strategies are the strategies that can help learners construct their own language systems and affect learning directly.Oxford （1989） believes that learning strategies are actions taken by learners in order to make language learning more effective，interesting and autonomous.Ellis （1994） suggests that learning strategies refer to the psychological behavior or action associated with a particular stage in the whole language acquisition or language use process.

2 Classification of learning strategies

Oxford （1990） classifies learning strategies into direct strategies and indirect strageies.The former is divided into memory strategy，cognitive strategy and compensation strategy.In contrast，indirect strategies “provide indirect support for language learning through focusing，planning，evaluating，controlling anxiety and other means” （Oxford，1990：151）.Indirect strategies are divided into three sub-categories： metacognitive strategy，affective strategy and social strategy.

According to the theory of cognition，Chamot & O’Malley （1990） divide learning strategies into three types.Metacognitive strategies are used to evaluate，manage，and monitor other learning strategies and learning processes.Cognitive strategies are used in a language learning activity.The social affective strategies is only used to provide more opportunities to contact with language for the language learners.Among the three strategies，metacognitive strategy is higher than the other two strategies.

According to the purpose of using the strategy，Cohen （1998） divides learning strategies into two types： strategies of learning language and strategies of using language.The former includes identification，differentiation，organization，repeated contact of materials，conscious memory and so on.The latter includes retrieval，rehearsal，cover up，communication strategies，etc.

On the basis of the above categories，the fourth category is put forward by Wen Qiufang （1993） in her doctoral dissertation.She divides language learning strategy into management strategy and language learning strategy.Management strategies include the establishment of goals，planning，choice of strategies，self-monitoring，self-evaluation and self-adjustment.Language learning strategies are divided into traditional and non-traditional kinds.

The above points of view are varies but they all admit that the choice and application of any learning strategy is the process of thinking and learning of language learners’ metacognition or self-cognition，which are crucial to language learning.

3 Summary and Prospect

There are still a lot of controversy on the learning strategies of the definition，classification，training and many other aspects.Meanwhile，there are also some areas needed to be improved，such as the studies on the learning strategies in different teaching environment，the research on the training strategies of learning strategies，the study of the special differences of Chinese as a second language，etc.And all of these are the direction of our further study.

References

[1]Chamot，A.The learning strategies of ESL students.In A.Wenden & J.Rubin （Eds.）.Learner strategies in language learning[M].New York：Prentice Hall，1987：71-83.

[2]Cohen.A.D.Strategies in Learning and Using a Second Languag[M].London：Longman，1998.

[3]Ellis.R.The Study of Second Language Acquisition[M].Oxford University Press，1994.

[4]Oxford，R.L.Language learning strategies：What every teacher should know[J].Boston： Heinle & Heinle，1990.

[5]Rubin J.What the “good language learner” can teach us[J].TESOL Quarterly，1975（9）：41-45.

[6]Rubin J.Learner strategies：Theoretical assumptions，research history and typology[M].Wenden A，Rubin J.Learner strategies in Language Learning.Englewood Cliffs.NJ：Prentice Hall，1987：15-19.

[7]文秋芳.大学生英语学习策略变化的趋势及其特点[J].外语教学与研究，1996，（4）：43-46.