Gender inequality is still considered one of the major social issues in China. While gender inequality in the Chinese education system has been mitigated to some extent, it can still be observed in authoritative teaching materials such as textbooks, hindering the development of students' gender awareness. Hence, the purpose of this paper is to investigate how gender inequality manifests itself in secondary school textbooks in the context of the traditional idea of value in modern China. Gender stereotypes in terms of occupational roles and personality, and gender bias against the contribution and ability of female characters are all identified in the English, History and Mathematics textbooks examined. On this basis, this paper finds that the implicit gender inequality in textbooks can be attributed to the bias imbued in Confucianism-one of the traditional cultural value systems in China. Finally, after negative impacts on students are identified, this paper suggests possible improvements to gender inequality in textbooks.