An experimental investigation of the performance of a wave energy converter of wavestar type was conducted. A PTO system of downscale is difficult to directly apply in the model test because the experiment in the wave basin is based on Froude scaling. In case of the hydraulic PTO system, modelling of oil pressure and accumulator is more difficult in the wave basin test. To overcome the limitation of modelling of hydraulic PTO system, new model test technique was applied in this study. The model tests were performed in regular and white noise waves, and existed model test technique and new model test technique were compared in each other. From the results, characteristics of new model test technique were introduced.