To study the unique syntactic complexity features in the ESP written texts and the textual functions realized by those syntactic resources, An ESP corpus is built, based on which a contrastive analysis of ESP and EGP text is conducted by adopting the framework of mufti-dimensional analysis. Results show that compered with EGP,ESP text is significantly different from EGP in syntactic complexity and textual dimensional features. In ESP texts, syntactic complexity can significantly predict the degree of textual interactivity, referential explicitness, overt persuasion and the online informational elaboration. This study demonstrates that differences on syntactic levels among texts from different registers are conducive to the realization of textual functions.