Abstract: For offshore wind turbines (OWTs) approaching the end of their design service life, repowering represents a preferred strategy through the integration of modern and high-efficiency turbines. This approach not only maximizes the utilization of existing foundations but also markedly enhances energy efficiency, providing an effective pathway for the sustainable reutilization of aging wind farms. In light of the engineering practice posed by repowering jacket-supported OWTs, this study conducts a series of centrifuge shaking table tests on a tripod bucket jacket foundation embedded in saturated sand. The objective is to systematically compare the seismic response of the OWT system before and after the repowering strategy. This study employed white noise excitation and seismic motions with varying amplitudes to evaluate key parameters, including natural frequency of OWTs, excess pore water pressure accumulation, acceleration response, and deformation characteristics of both OWT systems. The results indicate that, due to the increased nacelle mass introduced by the upgraded OWT structure, the repowered system exhibits stronger inertial motion under seismic excitation, leading to higher levels of accumulated excess pore pressure in the surrounding soil, increased peak rotational deformation of the tower, and amplified acceleration responses. Additionally, under the combined effects of additional stress and constraint from the bucket, the soil inside the suction bucket exhibits lower acceleration response and pore pressure accumulation than the soil outside the bucket, with partial filtering of the high-frequency components of the acceleration response. Moreover, the repowering strategy substantially amplifies the horizontal rotational deformation of the OWT but has a relatively limited effect on the vertical settlement. These findings provide important theoretical support for evaluating the seismic performance of repowered OWT systems.