In this study, we present a concept design of a Tension Leg Platform (TLP)-type Ocean Nuclear Power Plant (ONPP) using System-integrated Modular Advanced ReacTor (SMART), which is the most recent Small Modular Reactor (SMR) in the Republic of Korea. In order to mount SMART on the TLP platform effectively, we define design requirements and design variables, and perform a modularization and rearrangement of the SMART and other facilities. We focus on maximizing the advantages of TLP and SMART. Finally, we introduce a construction plan that covers from fabrication to installation and a new total General Arrangement (GA) of a TLP-type ONPP.