本研究提出一套英文句子文法升級系統，能針對輸入句子生成文法結構更進階的改寫版本，且同時保留原句語意，並提供文法解釋。該系統結合生成式人工智慧技術與英語分級語法資源，專門為第二語言學習者設計，旨在促進其寫作能力的提升，亦可作為文法學習的輔助工具。我們依據英語分級語法資源建立訓練資料集，並對預訓練的語言模型進行微調，以實現語法升級的目標。初步評估結果顯示，此方法能有效生成具可行性且符合教學需求的升級句子，對提升學習者的寫作表現具有正向幫助。

We introduce a method for generating a syntactically more advanced sentence for a given sentence, while preserving its original meaning, and providing a brief grammar explanation. In our approach, pairs of basic and advanced sentences are generated, using a generative AI system and graded grammar resources for second language learning. The method involves constructing a training set of aligned sentence pairs across the Common European Framework of Reference for Languages (CEFR) levels, fine-tuning a pretrained large language model. At run-time, input sentences are passed through the fine-tuned model to generate syntactically more advanced sentences and corresponding grammar explanations to support learning. We present a prototype system, GrammarUp, that applies the method to a generative AI system and the English Grammar Profile (EGP). Evaluation of a set of learner sentences shows that the method generates reasonable results useful in a writing development setting. Our methodology cleanly supports combining generative AI and expert grammar knowledge, resulting in an innovative grammar tutoring system for second-language learners.