Abstract: Based on the researches of Halliday’s systemic grammar in China and in respects of systematology, the paper tries to probe the scientificity of Halliday’s view of system, which is embodied by his systemic grammar. The validity of his methodology is affirmed and the limitations of his systemic description of language which is determined by his methodology and the nature of language, is explored. How the systemic description of language to reflect the practical function of language is evaluated.