In L2 writing, grammatical metaphor (GM) serves as a resource in such research dimensions as discourse-semantic construction, discourse-semantic functions，linguistic complexity, interlanguage development and academic writing. With meaning as the core to bind context and lexico-grammar, GM is a semiotic resource provided by systemic functional linguistics for semantic construction in written discourse. It demonstrates discourse-semantic functions of coherence, abstraction, and micro-semantic functions. Its properties, such as semantic complexity and fitting itself for the need of communicational complexity of high-level discourse writing, reveal itself as a resource to bind discourse-semantic construction of specific contextual types and language complexity. Interlanguage and academic writing also develop with GM as resource. Studies in L2 writing under the framework of GM are essentially meaning-centered; therefore, writing pedagogically should be based on discourse-semantic construction, i.e. write for meaning fitting into the context of particular types of writing task, by using the resource of GM.