In the early 1980s, on the base of Dulay and Burt’s theory, the American linguistician Krashen put forward his famous model, which is called The Monitor Model. Krashen’s Monitor Model has enjoyed considerable prominence in SLA research. The Monitor Model consists of five hypotheses: the acquisition-learning distinction, the natural order hypothesis, the monitor hypothesis, the input hypothesis, and the affective filter hypothesis. In affective filter hypothesis, Krashen attempted to evidence that affective factors could have a strong influence on second language learning. He summarized his second language teaching experience and realization, and he pointed out that affective factors that relate to SLA can mainly be pided into three categories: (1) Motivation: Whether a learner is purposeful or not will directly affect the learning result. The more purposeful the learner is, the stronger the motivation he has and the quicker he will progress; (2) Self-esteem: If a learner is confidence and feel good at himself, he would make great progress in second language learning and; (3) Anxiety: It states that ‘acquisition’ takes place as a result of the learner having understood input i.e. learners’ with high level of anxiety will be a little beyond the current level of his competence.(c.f. Ellis, 1985:262) In other words, learners with strongly motivation, adequate self-confidence, and with low level of anxiety, the effect of affective filter is weak. On the contrary, those who with a generally low level of motivation, poor self-confidence, and with high level of anxiety, will be influenced by affective filter. As a result, they could not get a good effect in second English learning.

2.2 The Study on Affective Factors in China
In our country, the research of second language learning started comparatively late. It was not noticed until 1980s. The majority of the domestic scholars at that time engaged in the introduction and comments of foreign research results about SLA, such as Zhuangling Hu, Chuming Wang,  Shichun Gui, etc. (c.f. Lianrui Yang, 2007:18) The research during that period of time established the foundation for the future researches on SLA.

In 1990s, with the comprehensive introduction and absorption of foreign research results about SLA and the combination with our own actual situation, domestic scholars conducted a series of targeted researches, such as Runqin Liu, Qiufang Wen, Lianrui Yang, Zhe Li, ect. (c.f. Lianrui Yang, 2007:171) Studies of this phase had a characteristic i.e. the main content of the research was to discuss the influence of learners’ cognitive, affective, and strategic factors and the object of the study gradually began to be transferred to learners. Such as Applied Psycholinguistics: The Psychological Research for Foreign Language Learning by Chuming Wang in 1990. They tired to analyze the key factors which influenced second language acquisition from the aspect of cognition and affection.

In early 2000, studies on affection factors in second language acquisition started to be more and more popular and became gradually mature. Dingfang Su(2004) , China's famous cognitive linguistics expert, published his English Language Teaching: Problems and Strategies, and discussed the impact of motivation in foreign language learning. Obviously, the exam-oriented education has some disadvantages. One of the biggest drawbacks of it is that the learning purpose of the majority of the students is to pass the exam. A substantial part of students have a low quality of motivation, the majority are lack of interest and confidence about learning English well. They often found themselves very frustrated by poor test scores and little improvements. To some extent, English tests largely contributed to students’ advancement and success in second language learning. But on the contrary, once the examination become not a motivation but a pressure, panic, fear, anxiety, or depression will be generated which will produce the opposite learning result. Meanwhile, he put forward the students-oriented eduction, where the philosophy dictates that (c.f. Dingfang Shu, 2004:32) we should take learners’ inpidual factors into account in English teaching and learning. 二语习得中的情感因素在英语阅读中的作用(4):http://www.youerw.com/yingyu/lunwen_9638.html