Butzkamm is one of those who strongly oppose the exclusion of mother tongue in the foreign language class. He argues that mother tongue, as a cognitive and pedagogical resource, is the greatest asset people bring to the task of foreign language learning.
The use of mother tongue in the foreign language class has also drawn Chinese researchers’ attention. Some of them focused on theoretical justification of the positive role of mother tongue, while others conducted empirical studies producing qualitative results. Bo explored code-switching in English classes and found that English-Chinese switching was prevalent. Similarly, as the theoretical studies advocate, most of the empirical studies reported mother tongue use in ministering the class, grammar and words instruction, and several other contexts.
2.2 Theoretical Background
The definition of “language transfer” occurred first in Lado’s Linguistics Across Culture in 1957. Lado thought that in the environment of the second language acquisition, learners depend on their mother tongue and transfer the language form, meaning and the culture related with their mother tongue to the second language acquisition.
There are two forms of language transfer: negative transfer and positive transfer. When there is difference between mother tongue and the target language, the negative transfer occurs. The negative transfer is mainly negative and will lead to language errors and the occurrence of difficulties in language acquisition. It will prevent learners from acquiring new knowledge. Ellis pointed out that in the first step of the second language acquisition, learners often depend on their mother tongue because of their lack of enough knowledge of the target language. In this step, there may be more negative transfer of mother tongue. When the rules of mother tongue and the target language are the same, the positive transfer may happen,and promote the study of new knowledge.
This paper analyzes the relationship between mother tongue and second language acquisition and emphasizes on the positive transfer and its role in second language acquisition. The study and analysis in this paper show that mother tongue plays a positive role in second language acquisition and is an important factor to promote second language acquisition.
2.3 Situation of     Mother Tongue Using in English Class 中学英语教学中母语运用研究(3):http://www.youerw.com/yingyu/lunwen_9792.html