An ocean thermal energy conversion (OTEC) system includes a working fluid pump, an evaporator, a turbine, a condenser, and a working fluid. The evaporator is connected to the working fluid pump. The turbine is connected to the evaporator. The condenser is respectively connected to the turbine and the working fluid pump, and located in a sea area below sea surface. The condenser includes a condenser main body and a deep sea water pipe. The condenser main body is respectively connected to the turbine and the working fluid pump. The deep sea water pipe is connected to the condenser main body, and has an inlet end and an outlet end. The deep sea water pipe is connected to the condenser main body via the outlet end. The working fluid flows between the working fluid pump, the evaporator, the turbine, and the condenser under the driven of the working fluid pump.