This paper dealt with the HVDC concept design of Cheju HVDC #2, which will be operated at 2011. The concept design is the first step of HVDC design procedures and the contents which were presented in this paper, are HVDC operation conditions based on the reliability of HVDC and AC network conditions, short circuit ratios(SCR) to related to HVDC stability and overvoltage and interactions between AC network including FACTS and generators, and HVDC system. The results of this paper are a keystone of HVDC #2 design.