We have proposed a direct-drive wave energy converter (WEC) device with a high-temperature superconducting tubular linear generator (HTS-TLG) adopted, and compared the design results of the HTS-TLG and the conventional TLGs, which suggests clear advantages of the HTS-TLG. In this paper, we focus on the mechanical structure of the WEC, the cryogenic cooling system of the HTS-TLG, and the relation between maximum output power and size of the heaving buoy. Besides, design results of a 2 megawatts (MW) HTS-TLG are compared to those of another counterpart, which verified that the proposed HTS-TLG has higher power density. In the end, induced voltage waveforms of the 2 MW HTS-TLG are also plotted.