This paper analyzes the content of “Arbitrary angle and radian system” in Chinese and American high school mathematics textbooks from macro and micro levels. At the macro level, curriculum standards and content range are compared, while at the micro level, concept learning, exercises and mathematical history are compared. The results show that compared with American mathematics textbooks, Chinese mathematics textbooks pay more attention to the cultivation of students’ “basic knowledge and ability” rather than inquiry ability. Chinese textbooks respect the logic of mathematical knowledge and emphasize the expression of mathematical language in concepts and exercises, while American textbooks are more reflective of real life. Chinese textbooks are more closely related to knowledge than American textbooks. Finally, some suggestions are put forward.