Using a binary-lambda-calculus based calculation method for complexity, we analyze and discuss the mathematical expressions and their complexity in two editions of the Chinese high school mathematics textbooks published by the People's Education Press. There is no statistically significant difference in the complexity of mathematical expressions between the two editions, and the differences are mainly in the interpretation of conceptual knowledge using mathematical expressions, as well as in the types of examples and their solution processes. Among them, the new edition uses changes of mathematical expressions to change the type of examples without increasing the complexity.