功能语法在20世纪六十年代由韩礼德发展壮大。它系统地提出了三大元功能理论，即概念功能，人际功能和语篇功能，为语篇分析提供了理论框架，可用以分析任何口头或书面语篇，以及任何单语、双语和多语语篇。本文旨在运用系统功能语法对《红楼梦》卷头诗及其五个不同英译版本进行分析，从三大元功能出发比较原诗和译诗在表达语篇的概念功能，人际功能和语篇功能时所采取手段的异同，衡量译文得失，同时检验系统功能语法在翻译研究中的可应用性和可操作性。研究表明，译诗在重现原诗的三大功能时，既有与原诗对等之处，也有一定的改写。改写的主要原因有：译者的误解和忽视；译者的改述；中英文差异性；以及译者追求押韵等。总而言之，系统功能语法适用于分析本诗及其翻译。

Functional grammar was developed by Halliday in the 1960s. It systematically proposes three core metafunctions--ideational metafunction, interpersonal metafunction and textual metafunction, which provides a theoretical framework for discourse analysis, and can be applied to analyze any oral or written discourses, as well as any monolingual, bilingual and multilingual texts. This thesis aims to analyze the subject poem of Hongloumeng and its five different English translations with the guidance of Systemic Functional Grammar, comparing the differences and similarities between the poem and its translations when expressing their ideational function, interpersonal function and textual function, and examining the applicability and practicality of SFG in translation studies. The research indicates that translations show both equivalences and shifts when reproducing the three functions of the original poem. The main reasons for the shifts include: the translator's misunderstanding and ignorance; the translator's paraphrasing; the inherent discrepancy between Chinese and English; and the translator's pursuit of rhyming. Last but not least, the research manifests SFG is applicable in the study of this poem and its translations.