The development of new information technologies has profoundly altered how personal data are collected and analyzed by states. This chapter explores the changes by focusing on the algorithmic turn of China’s citizen surveillance. We argue that citizens have been transformed into platform users in order to participate in surveillance, and meanwhile platform mechanisms like gamification have been increasingly embedded in China’s surveillance practices. These transformations, which we term “algorithmic turn,” routinely leverage the interactive features of digital technologies to move beyond the panopticon tradition that has long held the dominating role in citizen surveillance. Consequently, new technologies facilitate a fundamental shift in state surveillance: the subjects of surveillance are no longer passive citizens who are watched by the architectural design of the panopticon; they are instead platform users who actively participate in surveillance by generating personal data and monitoring their own and peers’ behaviors.