Objectives Aiming at a mooring system design with cost-effectiveness and high performance for wave energy converter (WEC) , the effects of such systems on the capability of power take-off (PTO) system and positioning performance of WEC are investigated. Methods A two-body floating point absorber is chosen as the sample WEC. The open-source WEC-Sim and MoorDyn codes are used to design two types of mooring system for WEC: one is a chain mooring system and the other is an integrated chain -rope (ie, polyester rope) mooring system. By performing time-domain analysis for the WEC with different mooring lines, the responses, such as WEC displacement, power take-off (PTO) and mooring line tension, are obtained respectively. Results The results show that, the effects of mooring systems on the displacement response of the floater are small, but these effects on the response of the spar body is obvious. For the WEC with a linear damper, these effects on the PTO response are negligible . Moreover, the line tensions of the integrated mooring system are lower than the corresponding tensions of the chain mooring system under the operational sea state. Conclusions The results of this study have reference value for the improved design of WEC mooring systems.