Previous investigation [1, 2] proposed that an introduction of water droplets into the film cooling air significantly improves the effectiveness of gas turbine blade. In order to allow comparison with experimental data, all the previous studies were confined to laboratory conditions. However, under typical gas turbine operating conditions temperature difference between the main stream flow (1561 K) and the coolant air (644 K) is approximately 917 K. The aim of this study is to numerically investigate the performance of mist assisted film cooling under the typical operating conditions of the gas turbine. Results showed the value of mist assisted film cooling effectiveness are greater than pure air cooling. Trajectories of droplets show that the water droplets vaporize faster. Typical percentage enhancement of the mist assisted film cooling effectiveness is 16% when the cooling air contains 6% mist with droplet diameter of one micron.