系統功能語言學認為語言具有其系統和功能，語文教學應該使學生掌握語言的系統，並在互動中學習如何恰當地使用語言。本文通過實證研究分析59位香港非華語學生的真實語料，結合量化數據和質性分析，探討第二語言學習者的實用中文寫作表現。研究發現，非華語學生整體實用文寫作能力較弱，尤其在語旨、語式、連接、文法等層面表現最弱；在語境內容方面普遍文類知識不足，無法掌握特定文類的寫作目的和結構，文步和層次不完整，亦缺少語境的概念；在表述方式層面詞匯量有限；在文法呈現方面受到英文文法影響，體現了語言的負遷移現象。本研究亦通過基於系統功能語言學發展出的寫作評估標準，為寫作評量提供新的視角，使教師和研究者能更細緻地了解非華語學生的寫作難點和學習需求，掌握學生到底是在語境內容、表述方式或文法呈現當中的十四個層面有甚麼不足之處，才能進一步發展有針對性的教學設計，通過相應策略提升第二語言學習者的寫作能力。Systemic functional linguistics emphasizes on the system and functions of language, and it suggests that language education should help students learn the system of language and how to apply it in communication appropriately. This empirical research analyzed the authentic materials of 59 non-Chinese speaking (NCS) students through quantitative and qualitative analysis. The research findings discovered the weak performance of NCS students in practical writing, especially in the aspects of tenor, mode, conjunction, and grammar. Other problems included the insufficiency in the genre knowledge, inability to understand the writing purpose and structure of certain genre, incomplete steps and phases, lack of the concept of context, limited vocabulary, and the language form affected by English grammar as the result of negative transfer in second language. This research not only studied their practical writing performance but also introduced a new scoring scheme of Chinese writing developed based on systemic functional linguistics. Therefore, teachers and researchers can understand students' writing difficulties and learning needs from the perspectives of context, discourse, grammar and presentation, and develop specific teaching design or relevant strategies to improve the writing ability of second language learners. Copyright © 2021 香港中文大學香港教育研究所.