Methodology of sociolinguistics is different from traditional structural linguistics, in particular, from the Chomsk's transformational-generative grammar.The distinctive methodological feature of Sociolinguistics is to analyze language elements in the speech communities with qualitative and quantitative approaches.In the earlier studies, sociolinguists paid much more attention on spoken forms because these forms could be analyzed in the speech communities and be easily explained from the relationship between language variables and sociolinguistic variables such as ethnic group, age, social class and gender.On the contrary, the study of written forms got inattention because they could not be researched as fully as spoken forms.Collecting data from the literatures, which is the traditional method used in exploring written forms in sociolinguistic, had restricted it form further development.Corpus and corpus-based approach has turned out to be useful in the study of written language since they emerged.With the use of corpus approach, a large number of achievements have been made such as in the studies of gender language, Chinese speech communities words in mainland China, Taiwan, Hong Kong and Macao, Chinese register, and discourse analysis.These studies are pioneering ones and have accumulated experiences for the future study, but they are still limited and need to be improved in some sense.The result of loanwords studies by Su (2010) shows that 134 Chinese phonetic matching loanwords, one percent of the total loanwords in A Dictionary of Loan Words and Hybrid Words in Chinese (1984), have already been replaced by Chinese indigenous words, but this finding was not testified by the contemporary Chinese corpus.The result of the reexamination of the changing histories of 134 Chinese phonetic matching loanwords by using the Contemporary Chinese Corpus established by State Language Committee of PRC supports Su's finding and reinforces the function of corpus approach in analyzing the trends of language change.Another fact that 119 Chinese phonetic matching loanwords have zero frequency when they were searched in this corpus suggests that there are some limitations in corpus, such as it is unbalanced with time spans or no Chinese phonetic matching loanwords is tagging in this corpus.Before using corpus and corpus approach in sociolinguistic studies, one should understand the comprehensive functions of corpus and what and how corpus can help the research in sociolinguistics.In addition to representativeness，balance and good distribution as a general corpus has, the corpus sociolinguistics needs should have: 1)Universality, namely including various styles or registers, various language variants from different domains and different regions|2)much more sociolinguistic information about language producers such as ethnic group, age, social class and gender, part of which should be able to be attained from sociolinguistically annotation|3) sociolinguistic annotation.If there is a better corpus, sociolinguistic studies with the help of corpus and corpus approaches will enhance a perfect combination of qualitative analysis and quantitative analysis.