This study demonstrates how native and learner corpora can enhance modal verb treatment in English-as-a-foreign-language (EFL) textbooks used in mainland China. Data analysis compares modal verbs in the textbook and native corpus by referring to distributional features, semantic functions and co-occurring constructions; and the analysis of the learner corpus refers to the use/misuse of modal verbs. A corpora comparison considers the authenticity of textbook language; and examination of learner use/misuse of modal verbs provides a learner perspective for textbook presentation that is applicable to learning difficulties. In this regard, this study highlights discrepancies between textbook treatment of modal verbs and authentic modal use in constructions, distributions and semantic functions, and its application of error analysis reveals inter/intra-linguistic interference in the use of modal verbs. This study can thus contribute to a corpus-informed and learner-centered design of grammar presentation in EFL textbooks that enhances the authenticity and appropriateness of textbook language for target learners.