In this paper, we presented a new analytical model for the transconductance and output conductance of submicron gate-length GaAs MESFET transistors. After an analytical study of the current voltage characteristics, the transconductance and drain conductance mathematical expressions are determined as a function of the drain and gate voltages in different operations regimes (linear, non-linear and saturated). In this frame, we elaborated a numerical simulation based on the different expressions established previously. It is shown that good agreements are obtained between the proposed model results and those of the theory, so the present model can also be employed for the computer-aided design of the logical and analogical circuits containing the submicron GaAs MESFET's.