This paper was carried out design of 600 V GaN power MOSFET Modeling. We decided trench gate type one for design. we carried out device and process simulation with T-CAD tools. and then, we have extracted optimal device and process parameters for fabrication. we have analysis electrical characteristics after simulations. As results, we obtained 600 V breankdown voltage and $0.4;m{Omega}cm^2ultra$ low on resistance. At the same time, we carried out field ring simulation for obtaining high voltage.