The introduction of modal verbs in English textbooks across levels in China was surveyed and compared with Chinese learners' use in writing to explore the potential impact of textbook introduction on learners' real use. The results have revealed: (1) divergences between the sequence of modal verb presentation in textbooks and their frequency order in native speakers' use, the unusual lower coverage of WOULD and early introduction of SHALL in particular; (2) the imbalanced coverage of different forms and senses of modal verbs in textbooks, notwithstanding that learners deploy some senses or forms in writing even if these usages have not been introduced; and (3) the constrained way of introduction -- English to Chinese translation in vocabulary, simple explanation and exemplification in sentence context. Core senses and fundamental forms introduced early in textbooks are used most frequently in learners' writing. Modal verbs with the perfect aspect structure and their associated senses introduced in textbooks at university levels rarely occur in learners' writing even at advanced levels. Limited agreement between textbook introduction and learners' use has been detected.