Early in 1870‟s, Dulay and Burt had proposed the Affective Filter Hypothesis and explained its influence on the foreign language learning process. Later, Krashen(1982, P. 31) developed and made the hypothesis perfect. He put the theory into five central hypotheses in second language acquisition (hereafter SLA), namely, the Acquisition-learning distinction; the Natural order hypothesis; the Monitor hypothesis; the Input hypothesis and the Affective Filter Hypothesis. Krashen argued that affective filter is a kind of psychological obstacle that prevents language learners from absorbing available comprehensible input completely. He looked affective factors functioning as a filter that reduces the amount of language input the learner is able to understand. It has a close relationship with the language learner‟s input and intake. It can be said that affective factors determine the proportion of language learners‟ input and intake. The affective factors include certain emotions, such as motivation, self-confidence, anxiety, and so on in the process of acquiring a second language. These negative emotions prevent efficient processing of the language input, and on the contrary, the positive emotions promote the efficiency of the process