Corresponding to the input hypothesis of Krashen, Swain proposed the output hypothesis. According to the ideas of Swain, people inclined to pay attention to the understanding of the meaning during the process of input but they would not be aware of the expression of forms. Only through the ways of output, the learners could be promoted to process the formal meaning instead of the simple semantic processing.

During the process to study Chinese, we people had the experience that it was difficult for them to repeat the complete words of the speakers if we understood the general meaning of the speakers. The fact was that we mainly focused on the contents of the talks of the speakers when we were listening. Unless we were told in advance that we had to repeat the words of the speakers, we would not only focus on the meaning of the words of the speakers but also the formal expression of the words. Another experience of the learning process was that we totally understood the main ideas of the emails from a foreigner when we were reading emails. However, we might encounter another problem. We had to send an email which had the same meaning as the one we had read days ago. Nevertheless, we could not remember the exact expression of a certain phrase. We might regret that we had not written down the expression of the phrase since we had paid our attention to the understanding of the contents of the email.

Thus, it was not enough to passively get input of a language. The learners should make use of every chance to apply the input resource to meaningful practice. The hypothesis got the point that the learners should actively utilize every resource to practice the use of language. The preliminary learners may want to know how to learn Mandarin, and then the method was that they should spare no effort to practice their written and oral Chinese.

The significance of output learning method could be summarized as the following three points. First, output learning could encourage the learners to try new ways to learn target language. Second, output learning could promote the learners to learn from others who had the same or above level. Third, output learning could make the learners be aware of the language level and the gap between others to improve their language level consciously and actively.