This paper examines the documentary under the dome and other alternative communication practices through the lens of media activism. The author argues that some media activism trends are emerging in the collective actions in present china, whose theoretical bases are new social movement theory and sources mobilization theory. The Chinese media activism mainly takes the tactics of supervising, spilling over, accessing and alternative media, and has different characteristics of instrumental, temporary, individual and practical from the political, persistent, public, and theoretical of the west. The media activism in China shows important values in the field of promoting public expressing, democratic decision making, civil rights protecting and enhancing soft power of international communication of China, and deserving theoretical and practical response from the lens of development communication.