Abstract: The Central Western Pacific is a key area for study of the tectonic evolution of a trench-arc-basin system. The geological features and tectonic evolution of the region have raised great attention from geologists. In this paper, the lithospheric effective elastic thickness (Te) is used as a parameter for understanding the tectonic-magmatic processes of the region and the Moving Window Admittance Technique is adopted as the major tool to calculate the Te for the study region, which considers both the surface and internal loads in a flexure model. The calculated results show that the Te values in the Central Western Pacific vary from 0～50 km, and the variation is closely related to major tectonic boundaries, and agrees well with tectonic provinces of the study area. In general, the Pacific Plate is characterized by high Te up to 25～30 km. Te values are relatively low in the submarine volcanic area (15～20 km). The noticeable reduction of Te is observed on the subducting plate from the outer rise to the trench axis of the Mariana Trench and the Philippine Trench, suggesting that the lithosphere is weakened from the outer rise to trench. The lithospheric strength in the western part of the Parece Vela Basin is weaker than that in the eastern part, possibly related to the asymmetric spreading of the basin. The lithosphere of the Caroline Plate is characterized by relatively uniform low Te values. The lithosphere in the Eauripik Rise, Caroline Ridge and Sorol Trough vary around a Te of 3 km, resulted from strong volcanism.