Increasing the temperature of working fluid is necessary to increase the efficiency of a gas turbine, although it is essential to cool down the system with cooling air to ensure the life expectancy and stability of the gas turbine component in the high temperature environment. Because the flow rate of cooling air can decide the performance of a gas turbine, a proper amount of cooling air should be considered carefully. Therefore, an integrative technology that can simultaneously analyze the aerodynamic performance, secondary air system, and thermal/structural characteristics is necessary for the initial design stage. In this study, we develop the algorithm, which is conjugating aerodynamic analysis, flow network analysis for secondary air system, and 2D axisymmetric heat transfer analysis, and analyze an example turbine.