The present paper considers the motion and wave loads on wave energy converters (WEC) connected to large semi-submersible. Twenty-four wave energy converters of heave point-absorbing type are connected to the moored platform. The motions and loads on WECs are measured in the regular and irregular waves as well as the platform motions. The platform motions are compared with the numerical solutions based on the potential flow theory. The measured heave motions of WEC are also compared with numerical solutions based on the Eigenvalue analysis. Additionally, the measured WEC loads with different drafts and different locations are compared each other. Based on these results, characteristics of WECs connected to the large semi-submersible are discussed.