摘要：PandaX is a large liquid-xenon detector experiment usable for direct dark-matter detection and 136Xe double-beta decay *** central vessel was designed to accommodate a staged target volume increase from initially 120 kg(stage I)to 0.5 t(stage II)and eventually to a multi-ton *** experiment is located in the Jinping Deep-Underground Laboratory in Sichuan,*** detector operates in dual-phase mode,allowing detection of both prompt scintillation,and ionization charge through proportional *** this paper a detailed description of the stage I detector design and performance as well as results established during the commissioning phase are presented.