Writing is the most difficult in the four language skills, and can reflect a person’s level of foreign language. Syntactic complexity is an important indicator to measure second language learners' academic writing language performance. Existing studies have paid less attention to the analysis of syntactic complexity of Chinese PhD students’ course paper writing. Thus, this paper tries to investigate the differences in syntactic complexity of abstracts between papers written by Chinese PhD students majoring in Economics and Management and that of the expert writers of journal called Administrative Science Quarterly in same field and tries to find the reasons behind it. 60 abstracts were used as research materials, among which 30 abstracts written by experts were used as reference, and the 14 indices provided by L2SCA are used to analyze the syntactic complexity of the abstracts. The result shows that Chinese PhD students, compared with expert writers, are more eager to use long sentences and coordinate phrases in their writings. The use of subordinate sentences is less than that of expert writers. However, the proportion of complex nominals in PhD students’ writings is surprisingly higher than that of expert writers, which means the L2 writing course do help them in their academic writing. Therefore, the study recommends that balancing the use of short sentences and subordinate sentences, and enlarging the syntactic diversity be emphasized in academic English writing training class.