The passive markers are not necessary in Chinese passive expressions. But why do the passive markers appeare in Chinese, and why are the markers numerous in number and imperfect in Chinese dialects? The answer is hard to be found in the passive markers system itself. In this essay, it is believed that the appearance of the passive markers has a fundamental reason, simple and unified. In Chinese the word structure is SVO while the topic structure is topic-comment when a patient serves as the topic, the two structure may disagree. As result, pass...