4H-SiC(silicon carbide) MESFET large signal model was studied using modified Materka-Kacprzak large signal MESFET model. 4H-SiC MESFET device simulation have been conducted by Silvaco's 2D device simulator, ATLAS. The result is modeled using modified Materka large signal model. The device showed a I-DSS=270 mA/mm and a G(m)=52.8 mS/mm at V-GS=0 V, V-DS=25 V Through the power simulation at 2 GHz, the bias of V-GS=-4 V and V-DS=25 V, 10 dB Gain, 34 dBm(1 dB compression point) output power, 7.6 W/mm power density, 37 % PAE(power added efficiency) were obtained.