In this paper, a multi-body wave energy converter is studied in the frequency domain. The device consists of a semisubmersible platform and 21 buoys. A mode expansion method, with total number of 27 modes, is used to formulate the dynamic motions. Moreover, An idealized form of power take-off mechanism is considered. Ocean environment and its directionality is modeled by using a JONSWAP wave spectrum with directional spreading according to Mitsuyasu. The objective is to assess the performance of the device in absorbing the wave energy and its dynamic behavior in ocean waves with/without considering the effect of power absorption mechanism. The current analysis method has been found to be computationally efficient and easier to interface with structural code compared to the available standard procedures by means of multi-body analysis approach.