Purpose: The aim of this study was to investigate the position of ethnicity in formal and hidden curricula of the new secondary education system. Methodology: The present research method was qualitative analysis of content analysis which consisted of two parts. The first part of the research included documentary analysis and content analysis. The statistical population included 51 books in the field of humanities in the second secondary school. The research sampling method was purposeful sampling and the research sample included 6 volumes of history and sociology books of the second secondary school. The content analysis unit consisted of text, images, and textbook activities. To evaluate the content validity was used experts' opinion about the degree of coordination of the content of the measurement tool and the purpose of the research. On the other hand, in order to ensure its reliability, Scott method was used. Based on the obtained reliability coefficient (79) it was quite stable. In the second part of the research, the research method was qualitative and ethnographic, and various tools such as student journals, photographs, semi-structured and informal interviews and observation were used to collect research data. To analyze the data in this section, qualitative content analysis was used by Smith method. Finally, to ensure the accuracy of the findings in this section, Triangulation method and re-referral of data to participants were used. Findings: The findings of the research in the first part showed that only 4% of the three sections of the content from the reviewed books paid attention to the 22 desirable components of ethnicity. Also in data analysis based on Smith method in the second part of the research, various themes including ethnicity neglect, teachers 'ignorance, different teachers' expectations, ethnicity as a cause of discrimination and the consequences of ethnic discrimination appeared. Each of them contained several sub-themes. Conclusion: Based on the findings, it can be acknowledged that the place of ethnicity in the formal and hidden curricula of the new secondary school system has been largely neglected. Therefore, due to the multiplicity of Iranian society, it is suggested that the curriculums of the secondary schools be completely revised to cover the necessary components for multicultural education and ethnic diversity in Iran.