There are more and more bloggers, those who express their feeling, give their comments, and record their lives by means of blogs. After this new media caused a trend, this study discussed whether the blogger’s self-concept was changed. Research through questionnaire investigation method, and take the junior high school second grade students in Hsinchu for example. 416 copies of effective questionnaire are collected and went through SPSS analysis. The relationship to the blogger’s self-concept is discussed through five dimensions, the social network in reality, blog social network, genders, academic achievements, and the existence of the blog. The results showed, (1) the existence of the blog and blog social network have nothing to do with the self-concept; (2) the existence of the blog has remarkable difference to the social network in reality; (3) bloggers with different academic achievements have no remarkable difference on the blog social network, but social network reality. Further, we can get the conclusion, (1) the existence or the usage of the blog or change user’s self-concept obviously; (2) the blog is capable of keeping friendship; (3) the blog has the “filter” function. Even though people who use blog knew each other in the real life, but some factors which affected relationship in real life will filter through blog, and left the attractive subject on line.