本文借助优选论（OT）句法的框架，在基于VP为双层复合结构、NP内生于VP外论元、虚词there直接从词库读取、存现句中的NP为呈现焦点等假设之上，利用ALIGN-PRES-FOCUS, CASE_nom, OB-SPEC和FULL-INT的制约条件及其等级排列，对英语存现句进行了优选论分析。存现句中的NP内生于VP的外论元，从而获得主格形式，但呈现焦点对句法的制约条件ALIGN-PRES-FOCUS抑制了VP后NP的提升，从而使其格位无法获得标记，违反CASE_nom。为了使句式满足OB-SPEC，说话者可以从词库中直接读取虚词there，或者提升方位短语LP，用于填充IP的标志语位置。

Under the framework of Optimality-Theoretic syntax (OT syntax) and on the basis of the hypotheses of double shell of VP, internal generation of NP within VP as the external argument, direct numeration of the expletive there from the lexicon and NP as the presentational focus in the existential clause, the article proposes an OT analysis of the English existential clause by resorting to such constraints as ALIGN-PRES-FOCUS, CASE_nom, OB-SPEC and FULL-INT and their hierarchy. The article argues that the NP in the existential clause is internally generated as the external argument of VP, and is thus endowed with the nominative case, but ALIGN-PRES-FOCUS, a pragmatic constraint on syntax, prohibits the raising of the NP following the VP, which, as a result, causes the unmarking of its nominative case on the surface form and the violation of the constraint CASE_nom. In order to meet the condition of OB-SPEC, either the expletive there is selected from the lexicon or the locative phrase is raised to fill the position of the specifier of IP.