AbstractA coaxial double-column wave energy converter (WEC) has been studied in this paper. The wave force of the floats and the hydrodynamic coefficients are solved by a semi-analytical solution method. We built time- and frequency-domain models and calculated the motion characteristics and power generation of the coaxial double-column WEC through the commercial software HydroSTAR and Intel Fortran. We use computers to build models of many different parameters and study the effects of different parameters on the motion performance and power generation capabilities of the device. They show that changing the diameter ratio of the upper float to the lower float can increase the output power of the device, and the smaller the diameter ratio, the larger the output power can be obtained. We also changed the depth of the damper plate and found that the deeper the damper plate, the higher the output power of the device. However, in general, the depth of the damper plate has no significant influence on the output power of the device.