This study aims to reveal the cognitive demands of senior high school English as a foreign language textbooks in China and their potential impact on students' thinking development. To achieve this, the study employed content analysis, using an analytical framework adapted from the revised Bloom's taxonomy, to examine the cognitive demands incorporated in the activities across nine target textbooks from three different publishers. The study found "Understand" to be the most common cognitive demand in the examined textbooks. However, it also identified that lower cognitive demands "Remember," "Understand," and "Apply" were less prevalent than the higher demands "Analyze," "Evaluate," and "Create." Additionally, the study observed variations in the distribution of cognitive demands within the textbooks for 10th, 11th, and 12th grades. Despite these variations, the distribution of cognitive demands across the three grade-level textbooks was found to be remarkably similar, with an increase in the occurrence frequency of cognitive demands "Apply," "Analyze," "Evaluate," and "Create," and a corresponding decrease in the occurrence frequency of cognitive demands "Understand" and "Remember." These findings indicate that senior high school English as a foreign language textbooks in China are intentionally designed to accommodate the thinking skill needs of students at each grade level and to promote the development of their thinking skills, with a particular emphasis on higher-order thinking skills. The findings hold significant implications for the design and use of language textbooks, highlighting the importance of integrating appropriate and challenging cognitive demands to effectively support students' thinking development.