The departure point for this thesis was a national online debate on Chinese sex education. In spring 2017, beginning with a mother complaining about the “explicit” contents in a sex education textbook on Sina Weibo, thousands of Chinese netizens joined in the discussion about the textbook – Zhen’ai Shengming and sex education for the Chinese youth in general. The netizens were divided into two camps. Some of them criticized the textbook being problematic and misleading, while others regarded Zhen’ai Shengming as the best sex education textbook ever in China. The heated online debate made me wonder if there was something at stake in sex education in present-day China. Consequently, I choose to study the textbook by asking, what kinds of understanding of sex and sexuality are presented in the textbook? What kind of different readings does it open up for? Can different readings reveal some of the tensions and dilemmas in sex education in China today? In order to explore these questions, I looked into two issues in particular: 1) the discourse of desire and pleasure, and 2) the sexual orientations and relations presented in the textbook. By studying the textbook, I aim to use it as a case for investigating the complex issues at play in the sex education in present-day China. For understanding the textbook, I have situated it in the contexts of the Chinese sex education tradition and the social transformations in China in the reform era. With a close reading of the debated textbook, I find that even though the textbook can be regarded radical in the Chinese context, there is also a marked continuation of the disciplinary aspects – but in a less directive way compared to the earlier sex education. Thus, the book may be seen as a compromise between the new sexual culture and the continuous need for controlling young people’s sexuality by the state. Drawing on Foucault’s understanding of knowledge and power (especially bio-power), I argue that the textbook can be regarded as an example of the modern disciplinary power that functions through producing the “official knowledge” for shaping everyday practices and discourses.