In this paper an analytical drain current model in subthreshold region is proposed and can be used for MOS or PD-SOI transistors. The model can describe output current dependency on the drain voltage accurately as well as including short channel effects. The proposed model needs only two fitting parameters to predict the current of a transistor with very good accuracy and simply can be used in simulators. To validate the model, it is compared with two short channel MOS transistors with different technologies by HSPICE simulations.