The adjustment of syntactic and phraseological complexity is a key consideration in text adaptation. However, research on this topic in the context of Chinese as a second language (CSL) remains limited. Using 700 CSL reading texts graded following the newly issued Chinese Proficiency Grading Standards for International Chinese Language Education, this study examines differences in syntactic and phraseological complexity across texts of varying grade levels using 12 indices and assesses the predictive power of these indices for the grade levels of adapted texts. The results reveal that the 12 indices at the sentence, collocation, and phrase levels significantly differentiate the grade levels of the reading texts, with 11 showing medium to large effect sizes. Whereas all indices exhibit an upward trend overall, their specific patterns of cross-level changes vary. The strongest predictors of the grade levels of the texts are diversity of total collocations, mean length of sentences, and mean length of noun phrases. We discuss the implications of these findings for establishing syntactic and phraseological complexity benchmarks in CSL teaching materials, adapting CSL learning and assessment texts, and devising effective instructional strategies.