中文摘要：

现代汉语的一大类型特点是话题优先。为什么会有这个类型特点，却鲜有文献进行探讨。文章首先以古今汉语对比的视角，论证现代汉语的主宾语之间的不甚明显的对立关系，表现在话题化不需要复指代词回指，有丰富的去及物化手段以及表达语义对立的不同句式之间较容易转换，这些形态句法特点为现代汉语的话题化操作提供了便利，最后从英汉对比的视角论证了这个观点。

英文摘要：

The Modem Chinese is recognized as a topic-prominent language. But why it has such a typology is rarely investigated. This article, from the contrastive perspective of Old Chinese and Modem Chinese, has probed into the less perspicuity of subject and object, non-compulsoriness of self-copy pronoun in topicalization, the various detransitivization devices and the smooth transition among different sentence constructions with conflicting semantics in Modem Chinese. These properties pave the way for topicalization. At the end of the article, this argument has been further investigated from the angle of a contrastive study of Chinese and English.