In China, the promotion of sexuality education for children and adolescents is hindered by a relatively conservative culture and insufficient drive from the government. With the government and the market failing to deliver in this area, social organizations, such as the third sector, are playing an important role. This paper mainly discusses how Chinese social organizations promote sexuality education for children and adolescents on a large scale. This paper studied NW, the largest sexuality education support platform in China at present, and 16 frontline implementing organizations in its cooperation network. This research collects empirical data through participatory observation and semi-structured interviews, involving a total of 37 interviewees, plus relevant text data. The study follows the analytical method of process tracking, trying to extract the key mechanisms of how social organizations promote sexuality education from the processes demonstrated by the specific cases. This paper focuses on the key phases of a standardized sexuality education program, from its design to promotion and then to implementation. It is found that, based on the large-scale operation strategy, the operation process of the sexuality education program exhibited three core mechanisms: standardized program design, organizational cooperation network and administrative mobilization. These three mechanisms have become the key force to break through many of the cultural and institutional obstacles and achieve large-scale implementation of sexuality education. Finally, this paper discusses the challenges of operationalizing the sexuality education program, with compromised teaching quality as a major one, and points to the direction for future research.