The gender gap remains an issue in the biological education community. This study explores the extent to which an egalitarian gender ideology, encapsulated in five biological science textbooks for upper secondary schools in China, manifests through representational, interactive and compositional meanings of social semiotic theory. The findings reveal that females in the textbooks tend to be depicted as passive and inferior to males. More males are represented as playing pioneering and leading roles, as opposed to females, who are cast in assistant and subordinate roles in professional activities. The gendered messages delivered have the potential to disempower female students' career aspirations and adversely regulate their perceptions and projections of gender identities in biological science.