Chinese–English bilingual programs in China advocate using both English and Chinese in instruction. Mathematics teachers in these schools need to use English as the medium of instruction to achieve the learning objectives of the school mathematics curriculum and also meet the English proficiency goals. Mathematics textbooks play a crucial role in teaching and learning within such a learning environment. This study presents a comparative study aiming to examine how linear equation unit is arranged in secondary school mathematics textbooks (i.e., IB, IGCSE, and Chinese textbooks) in Chinese-English bilingual schools. It explores the similarities and differences in these three series of textbooks. Four aspects of linear equations in different textbooks are compared: the number of examples, the distribution of contents, the learning activities, chapter review exercises. The results show that the three textbooks have different approaches and priorities that emphasize the positions and weights of the linear equation unit. The textbooks in China contain the highest percentage of linear equation contents and pay the most attention to explaining and analyzing how to set the unknown variable and using the concept of the linear equation to solve real-life problems. The findings can enrich teachers’ and researchers’ knowledge of mathematics textbooks in international schools in China and put forward some suggestions to improve the effectiveness of using textbooks in such schools.