Abstract: Tridacna gigas is the largest marine bivalve, and its hard and dense aragonite shells usually have annual and daily growth lines, which have been demonstrated to be an ideal material for high-resolution paleoclimate research. The oxygen isotope has been widely used in Tridacna paleoclimate studies. However, the oxygen isotope of Tridacna shells must be accurately calibrated by modern geochemical process before paleoclimate reconstructions. Palau is located in the northwestern edge of the Western Pacific Warm Pool. Long-lived Tridacna spp. is a common species in the coral reefs of Palau Islands, which may provide abundant materials for paleoclimate reconstructions. In this study, we present a high-resolution oxygen isotope profile from the inner shell of a modern living T. gigas specimen PL-1 from Palau. The high-resolution chronology of the oxygen isotope profile is determined by the clear daily growth layers in the inner shell. The result suggests that the δ¹⁸O_c profile of the T. gigas shell has no obvious trend, indicating that the vital effects have no significant influence on the oxygen isotope of shell. Combining with the instrumental data, we found that the ENSO activities in the tropical Pacific had impacts on the regional hydro-climate changes of Palau, and left some fingerprint in the oxygen isotope of Tridacna shell. This study indicates that the daily growth layer and the oxygen isotope in the inner shell of Tridacna from Palau have the potential for high-resolution paleoclimate research.