Migrant workers constitute the main city workforce in China. However, they are the victims of social inequality. Sina Weibo is one of the most important channels for people to share information and public opinions. In order to study into the sentiment diffusion of social inequality over Sina Weibo, we collected a huge number of root microblogs and reposts based on the search query “Migrant Worker”. With applying the sentiment tendency analysis tool provided by Baidu AI, we were able to capture the sentiment flipping process. We found that most microblog users tended to follow the previous users’ sentiment polarity. But the intensity of the sentiment polarity would always get weaken.