This study aims to investigate the multidimensional relationship between Internet use，social capital，Internet activism participation based on the data of 2010 China General Social Survey. The results show that Internet use can positively predict the height，heterogeneity and universality of social capital. The height of social capital can positively predict Internet activism participation. The participants of Internet activism differ greatly from the participants of offline collective action. Actors with higher social capital，internet use and income are more likely to participate in Internet activism due to lower costs and risks，while actors with lower social capital，internet use and education may choose offline collective action which confronts higher costs and risks.