Through the reflection on Yong Chang Girl Student Suicide Event，this paper discusses the characteristics of public opinion and the social mentality of those who have no interest involvement with the event in mass incidents. The study has found that the main reasons for mass events with non-direct interest conflict occurrence and its public opinion evolution are as follows：the sense of deprivation due to social fracture，accumulated negative emotions resulted from intensified class polarization，panic，anxiety and anger caused by livelihood issues，public mistrust in the government due to its credibility loss，as well as antagonism and disputation of public opinion brought by social class stratification.