A number of studies have reported the cultural representations in English textbooks in many contexts, especially those in Asia. However, these studies relied on a small data set and the findings suffered severe limitations. To overcome such shortcomings, we self-built a corpus that has 40 volumes/books of over one million words to examine the cultural constellations evident in 10 sets of university English textbooks in China. With such a large corpus of 864 texts, which significantly exceeds the number of texts examined in previous studies, we intended to offset the weakness of manual content analysis in mining big data and thus also reduce subjectivity markedly. We subjected the whole data set to thematic coding through corpus tools. We found that: (1) the dominance of American/British cultures in these texts is prevalent, with the cultures of other Inner-circle countries in the periphery, and the cultures of the Outer-circle and Expanding-circle countries almost entirely neglected; (2) these textbooks showed little interest in local or Chinese cultures. We conclude by positing that the dominance of Anglo-American monocultural representation in English textbooks is problematic in an increasingly multilingual and multicultural world.