Through comparison of subjects among four languages: English, German, French and Chinese, discusion of subjectivation, agentivity and psychological,cognitive foundations of subject, we find that subject has its own psychological, cognitive and semantic foundations, grammar shows itself as simply the top of the iceber.

In Chinese,the front of the subject-predicate structure can be the thematized subject and adverbial,alao can be non-thematized sentence-initial subject and adverbial.

This paper mainly discusses the functions of thematization of adverbials as well as the relationship between thematic construction and sentence structure , and the difference between unmarked and marked theme.

With the aid of the relativized SUBJECT theory provided by Progovac (1992,1993), the author tested advanced Chinese learners in their acquisition of English reflexives in monoclausal sentences and discussed the process in which UG, L1 knowledge and L2 input all play significant roles.