Recently,register theory,one of the most important theories of systemic functional grammar,has been received scholars’more and more attention and widely applied into translation,which brings a new perspective for translation research and provides a reasonable and scientific way of evaluating.Fortress Besieged,written by Qian Zhongshu,contains rich content,uses special language,and adopts unique writing technique skills,which can be called the literary classic.The paper combines register theory with translated literary work and explores the equivalence of Fortress Besieged in the process of translating from field,tenor,and mode of discourse to achieve translation equivalence as much as possible,which can improve translation quality and promote the spread of Chinese culture.