In this paper, the effect of channel length and width on the large and small-signal parameters of the Graphene Field Effect Transistor (GFET) have been explored using an analytical approach. In the case of faster saturation as well as extremely high transit frequency GFET shows outstanding performance. From the transfer curve, it is observed that there is a positive shift of Dirac point from the voltage of 0.15 V to 0.35 V because of reducing channel length from 440 nm to 20 nm and this curve depicts that graphene shows ambipolar behavior. Besides, it is found that because of widening channel the drain current increases and the maximum current is found approximately 2.4 mA and 6 mA for channel width 2μm and 5μm respectively. Furthermore, an approximate symmetrical capacitance-voltage (C–V) characteristic of GFET is obtained and found that capacitance reduces when the channel length decreases but the capacitance can be increased by raising the channel width. In addition, a high transconductance of 6.4 mS at channel length 20 nm and 4.45 mS at channel width 5 μm along with a high transit frequency of 3.95 THz has been found that demands high-speed radio frequency (RF) applications.