In this study, a non-linear vibro-impact mechanism is integrated inside a semisubmerged cylindrical heaving point absorber in order to enhance its power capture by utilising the non-linearity of vibro-impact events. A piece-wise linear model is derived considering linear wave-buoy interaction and the non-linear vibro-impact mechanism. Since the dynamics and performance of the vibro-impact wave energy converter (WEC) are sensitive to design parameters, a parametric study and analysis are conducted numerically by varying the design parameters in a broad range to evaluate their influence on the vibro-impact WEC’s dynamics and performance, in terms of response amplitude operator, average power output and peak-toaverage power ratio. Numerical simulations show that there exist some optimal sets of the design parameters to achieve a trade-off among the aforementioned performance indices. Hence, the parametric study in this paper can give some basic guidelines for optimising and prototyping the design of the vibro-impact WEC for wave tank testing.