本文对合成方位词“之前”和“以前”进行对比分析。在句法特征上,二者都可以位于句首、句中、句尾和句间。此外“以前”还可以单独成句;二者都可以做主语、宾语、定语和状语。在语义特征上,二者在时间义与空间义、具体义与模糊义、长时义与短时义方面有些差异;在语用特征上,二者在文艺语体和新闻语体中出现频率最高。 In this paper, the contrastive analysis of the synthetic terms “before” and “before”. In syntactic features, both can be located at the beginning of sentences, sentences, sentences and sentences. In addition “before ” can also be a separate sentence; both can be the subject, object, attribute and adverb. In terms of semantic features, the two have some differences in meaning between time and space, specific meaning and ambiguous meaning, long sense and short sense of meaning. In pragmatic features, the frequency of their appearance in literary style and news style highest.