It is divided into four books for levels 1-3, 4, 5 and 6, including 8 language versions. Contains all outline vocabulary. Based on the sorting and analysis of HSK real questions over the years, words are divided into ultra-high-frequency words, high-frequency words, low-frequency words and zero-frequency words according to their frequency in the test. The example sentences refer to the real questions to help students understand the test site and focus on learning key and difficult vocabulary.