Abstract: Grammatical metaphor in the Hallidayan sense only comprises ideational and interpersonal metaphor, while Martin and others propose the inclusion of textual metaphor.Based on metafunctions of Systemic Functional Linguistics, this paper analyzes the current discussions of textual metaphor, pointing out that some textual metaphors by Martin and others are in essence representations of ideational and interpersonal metaphors in text, and some are not in accordance with the grammatical metaphor criteria.Four types of textual metaphor with dual functions are proposed from the perspective of relators in non-finite clauses: (1) elaborative non-finite clauses, (2) extensive and enhancing non-finite clauses without relators, (3) extensive and enhancing non-finite clauses with prepositions as relators, and (4) enhancing non-finite clauses with prepositionized non-finite verbs.