An improved gate current model of GaAs FET's is presented. A conventional gate current and the reverse breakdown characteristics. Conseguentli, the model has been determined only by the forward current model fails to fit measured results in the reverse bias range, under which power amplifiers operate. The proposed model improves this problem and shows a great enhancement in accuracy throughout the whole operation range of FET's. The model consists of three diodes and a resistor, which are standerd elements implemented in commercially available circuit simulators, and thus it can easily be used for analyzing performances of various FET circits.