When a large-scale offshore wind farm (OWF) is connected to a power system, the quality of the connected power system can be significantly deteriorated under different operating conditions. This paper presents the analyzed voltagevariation results when Taiwan Power System is connected with a large-scale OWF with different OWF capacities and various lengths of submarine cable. A commercial power-system simulation software is employed to simulate the results. The ultra-high-voltage buses of onshore substations that are close to the potential OWF are properly selected as the connection points. The voltage-variation results at the connection points under different lengths of submarine cable and OWF capacities are accomplished and analyzed when the OWF is connected to the selected buses. The simulated results can offer a reference for the development of OWFs in Taiwan in the near future.