The study investigates the vocabulary profile of a set of English textbooks "New Senior English for China," which is widely used for senior secondary education in China. It examines how the words required by the 2017 National English Curriculum Standard for General Senior Secondary Education in China are covered, repeated and distributed in the textbooks. The results show that the textbooks cover only about 80% of the lemmas required by the 2017 English Curriculum Standard. Among the lemmas covered in the textbooks, half of them are repeated less than five times in the textbooks. Most of the lemmas which recur more than five times in the textbooks have dispersion values above 0.5. Lemmas with dispersion values below 0.1 are mainly composed of theme-based words. Although the study indicates that some words are distributed favorably, the textbooks fail to provide sufficient coverage and repetition of the words required by the 2017 English Curriculum Standard. Therefore, extra exposure and repetition of these words are required for optimal learning.