The environmentally friendly behaviors of Chinese residents still remain at a low level and need to be further improved to cope with severe environmental problems. Using the 2010 China General Social Survey data, this paper explores whether social capital can be used as a lubricant to effectively promote residents' environmentally friendly behaviors, including private domain, public domain, and payment-oriented environmental behaviors. The results show that social network expansion has a significantly positive effect on all three types of environmentally friendly behaviors, while social trust and social equity are only closely related to payment-oriented environmental behaviors. This paper further introduces environmental cognitive variables as mediating variables to test the mechanism of the influence of social capital on environmentally friendly behaviors. In general, environmental knowledge, environmental concern, and environmental attitudes play important roles in the impact of social networks on residents' pro-environmental behaviors. This paper provides a reference for the government to take measures to encourage residents to participate in environmental protection.