This paper uses corpus linguistics to examine reading passages of an English textbook used in North Korean correspondence universities. The English textbook was compiled into corpora and processed using Antconc and The Complete Lexical Tutor. From the corpus, high-frequency content terms and a keyword list were extracted and compared to the BNC reference corpora. Additionally, the corpus was categorized into the GSL (General Service List) and AWL (Academic Word List). The findings are as follows: (1) the vocabulary in the textbook is more varied than that found in North Korean middle school or first middle school English textbooks. (2) The terms related to the “Kim Jong Il system,” “science,” “technology,” and “labor” frequently appeared in the texts and are classified as positive keywords. (3) About 93% of the texts contain GSL K1 and K2 words, whereas 2% of the texts have AWL terms. The results demonstrate that adult English education in North Korea is designed for those who have completed their education in general middle schools, with a focus on strengthening vocabulary and increasing word variety. This education is provided to workers so they can learn about science and become technologically savvy, thus upholding the country’s system.