In this study, a vibro-impact wave energy converter (VIWEC) is investigated to generate in-situ power for marine data buoys. A model of the VIWEC is proposed, which integrates linear wave-buoy interaction with the vibro-impact mechanism in a piece-wise linear way. Intensive parametric study and numerical simulations are undertaken to study the influence of design parameters on power capture performance, including the mean power, the pick-to-mean power ratio, and the capture width ratio. For a certain data buoy and its surrounding wave climate, numerical simulations indicate that the vibro-impact design parameters have a significant influence on wave power capture, and a properly designed VIWEC can provide sufficient in-situ power supply.