This paper presents the modeling and power quality analysis of Jeju island power system connected with wind farm, current source type HVDC system, and thermal power plant. It is for indicating the influence of wind farm operation in steady and transient state in Jeju island power system. For the computer simulation, four kinds of main items are modeled, which are 83(MW) wind farm, 300(MW) HVDC system, thermal power plant, and Jeju power load. To analyze the influence of the wind power generation to the Jeju power system, two kinds of simulations are carried out by using the PSCAD/EMTDC program. One is the steady state operation under the different wind speeds, and the other is the transient state operation when all of wind farms in Jeju island are disconnected from the Jeju power grid instantaneously due to the over wind speed than the rated value. These comparative studies are useful to analyze the influence of wind farms on the Jeju island power system stability.