We　presented　a　GaN　Schottky　diode　model　with　consideration　of　self-heating　effect　of　devices　in　operation.　The　impact　of　diode　chip　temperature　on　the　current　and　capacitance　was　taken　into　account　in　this　model.　The　thermal　resistance　of　diode　chip　was　extracted　by　simulation　combined　measurement　to　calculate　the　temperature　of　Schottky　junction　with　different　pumping　power.　Advantages　of　established　device　model　in　the　design　of　a　220GHz　frequency　doubler　were　presented　in　the　end.