This paper analyses two Chinese sex education picture books for children aged between 3 and 6 years of age using van Leeuwen's legitimation framework, which identifies four types of legitimation strategies: authorization, moral evaluation, rationalisation and mythopoesis. Our findings suggest that personal authority tends to be vested in mothers as the conveyers of sex education to young children. Moral evaluation is realised through values such as responsibility and love, which are embedded in the description of biological events and physical objects, implicitly instilling in children the accepted heterosexual moralities that pervade mainstream Chinese society. Rationalisation is used to suggest a general social need to decrease the degree of directness in discussions about sex-related knowledge and to legitimise the appropriateness of the contents of sex education for young children. With respect to mythopoesis, both texts present a moral tale in which the love and marriage of a man and a woman is rewarded by the birth of a 'healthy, strong and clever' child. All these strategies configure to construe a moderately open, highly positive and fundamentally stereotypically heterosexual image of sexuality and procreation for young children in mainland China.