Abstract: There are certain differences between the Sydney Grammar and the Cardiff Grammar which belong to Systemic Functional Linguistics.This paper aims to discuss extensions of the Cardiff Grammar over the Sydney Grammar in four respects concerning functional syntax and semantics.Through the comparison between the two models, the study indicates that the main extensions are reflected in the following four respects:(1) that the Cardiff Grammar bases the categorization of the "Main Verb Extension" mainly on its function, and that it recognizes more expounding items of the element than the Sydney Grammar; (2) that the Cardiff Grammar establishes different criteria from the Sydney Grammar with reference to the differentiation of different groups; (3) that the Cardiff Grammar bases the differentiation of different types of Auxiliaries on their distinct meaning;and (4) that the Cardiff Grammar semanticizes the Mood system network originating from the Sydney Grammar.