This paper analyzes the grammatical structures of code-switching in Qian Zhongshu 's famous work-Fortress Besieged and two conclusions are reached: In this novel, the matrix language Chinese plays a dominant role in the mixed constituents, lexically, morphologically and syntactically while in the matrix language islands and the embedded language islands, constituents respectively follow the grammatical rules of the matrix language-Chinese and the embedded language-English or French.
