For the purpose of text classification or information retrieval, we apply preprocessing to these texts such as stemming and stopwords removal. Almost all the techniques could be useful only to well-formed text information like textbooks and news articles, but is not true to social network services (SNS) or any other texts in internet world. In this investigation, we propose how to extract stopwords in context of social network services. To do that, first we discuss what stopwords mean, how different from conventional ones, and we propose statistical filters TFIG and TFCHI, to identify. We examine categorical estimation to extract characteristic values putting our attention on Kullback Leibler Divergence (KLD) over temporal sequences on SNS data. Moreover we apply several preprocessing to manage unknown words and to improve morphological analysis.