Abstract: A large-diameter and single-pile steel pipe is mostly used for the foundation of fixed offshore wind turbine. By reasonable modification, the single-pile steel pipe can be used as an energy capture chamber for Oscillating Water Column (OWC) wave energy converter. In this study a structural scheme of coupling the fixed single-pile foundation with the OWC device is proposed, which includes opening holes at reasonable positions of the underwater part of the single-pile foundation and installing diversion ducts, air turbines and vent pipes at the overwater portion of the foundation, thus forming an embedded OWC device. Because only the first-order energy conversion process in the OWC device is studied, the role of the back-end equipment like air turbines and generators is not considered, and instead, the vents are used for simulating the pressure drop produced by these back-end devices. In order to reveal the energy capture mechanism of the novel OWC device, the hydrodynamic performances of the OWC device under the cases of three types of open holes, i.e. square, elliptical and circular open holes and under the conditions of four kinds of open hole submergence depth ratios (d/h), i.e. d/h=0.13, 0.27, 0.40 and 0.53 and two kinds of hole opening degrees (s/S_c), i.e. s/S_c=0.054 and 0.042 are investigated through numerical simullation. The results indicate that the square open hole with a submergence depth ratio (d/h) of 0.13 and a hole opening degree (s/S_c ) of 0.054 can offer an optimal capture width ratio (ξ), reaching up to 0.23.