Abstract: In this paper, based on solving Poisson equation to the structure of Si/SiGe pMOSFET with polycrystalline SiGe gate, its threshold voltage model and I-V electrical characteristic model are proposed. The secondary effects induced by scaling of the MOS device, such as drain-induced lowering barrier effect (DIBL), short-channel effect (SCE) and velocity overshoot effect, are also taken in account. By simulating the model with Matlab, the relationship between threshold voltage and relevant parameters, such as Ge content in P+ Poly SiGe gate, gate length, oxide thickness, Ge content in relax SiGe virtual substrates, doping concentration and drain bias, are obtained. The results of I-V characteristic shows that MOS device with strained Si as its channel has higher output characteristic. Finally, the evidence for the validity of our model is derived from the comparison of analytical results with the simulation data from the 2-D device simulator ISE. The proposed model can also be easily used for reasonable analysis and design of small-scaled Si/SiGe pMOSFET.