既往关于PRO局域语义约束的语义界定和移位的句法界定，难以满足解释充分的要求。本研究通过将PRO和NP语迹及其他空语类进行对比后认为，PRO在语义上具备跨事件特征，是两个事件结构共享的主目语；在句法上执行先拼出，后删除操作。这样的句法语义属性界定具备题元和格的逻辑一致性。本研究有关PRO的句法语义属性设定，在汉、英、冰岛、基隆迪语特殊语例的分析中具备较强的解释力。

 The former studies deem that semantically, PRO forms local lexical binding relation to its antecedent. And syntactically, it is the trace after the move of its antecedent. However, this semantic and syntactic interpretation to PRO fails to satisfy the requirement of interpretive adequacy. The present study first compares PRO, NP trace and other empty categories and deems that semantically, PRO spans across different event structures and is the co-argument of two event structures and syntactically, PRO follows the derivational pattern of “first spelled out then deleted”. This designation of the semantic and syntactic feature of PRO satisfies the logical match between theta role and case. The semantic and syntactic features of PRO defined by present study can be better applied to interpreting some exceptional cases of Chinese, English, Icelandic and Kirundi.