This study examines the cultural contents in one textbook series, which is currently in use for English as a foreign language (EFL) education among ethnic Mongol junior high students in Inner Mongolia, China, to understand the representations of multiculturalism and underlying power relations that appear in them. Applying Kachru and Nelson's model of English spread and their categorisation into Inner, Outer and Expanding circles, this critical content analysis investigates which countries are introduced and how multicultural variables including race/ethnicity, gender/sexuality, social class, and people with disabilities are represented. The results show that representations of cultures of three circle countries and multicultural variables are shown in an unbalanced, stereotypical way and lack diversity. Additionally, we present the tensions within power relations among different countries, race/ethnicity, social classes, and gender/sexuality. The findings suggest that a critical multicultural perspective not only helps students and educators recognise both the international and internal diversity, but also urges educators and textbook writers to emphasise the importance of cultural knowledge of EFL textbooks to better serve ethnic Mongol students.