The capacitance-voltage characteristics and the variations of threshold voltage of strained Si1-xGe x channel p-MOSFET with Ge fraction are investigated via two-dimansional numerical simulation. The results indicate that with the increase of Ge fraction, the subthreshold current increases remarkably, and that the gate capacitance changes significantly when the device is in inversion, moreover, the Ge fraction dependence of the variation of threshold voltage is linear. Combining the change of the Si1-xGex channel length with the relevant physical model, the mobility of holes in channel is demonstrated to be inversely proportional to the derivative of the total resistances with respect to the channel length in a weak applied field.