THIS paper investigates the fractal features and functional variation of the language system from the perspective of Systemic Functional Linguistics (SFL). It first reviews the concepts of fractal and fractalization, elaborating on their significance as part of the SFL methodology in terms of categorization. Then, it reexamines some key concepts in SFL from the fractal viewpoint, analyzing the working mechanism of language fractalization. It is found that fractalization creates functional variation within the language system; also, fractalization plays a significant role in ontogenesis, phylogenesis and logogenesis. Finally, this paper discusses the social semiotic basis of fractalization of the language system and its implications to discourse studies.