In this article, flame liftoff height predictions have been carried out for diluted methane jet flames with high temperature and vitiated coflow. Three-dimensional mass, momentum, energy, and species equations are solved with modified k-epsilon and modified k- turbulence models to predict the behavior of lifted jet flames. The effect of turbulence model parameters, fuel jet velocity and coflow velocity has been investigated for jet flames. The flame is assumed to be quenched when the fluid time scale is less than the chemical time scale (Da=f/ch1). The predicted results show that substantial premixing of fuel occurs with surrounding oxidizer in axial and radial directions. Predicted flame liftoff height agrees well with the experimental measurements at 100m/s jet velocity and it is significantly higher than the predictions reported in earlier work. However, predicted variation of flame liftoff height with jet velocity agrees well with Kalghatgi's (1984) nondimensional parameters. The flame liftoff height, temperature distribution, species distribution, and velocity distributions in radial and axial directions are in good agreement with the experimental results.