According to the model of ionized impurity scattering, acoustic phonon intravalley scattering and optical phonon intervalley scattering, the dependences of electron mobility of strained Si/(001)Si1-xGex with different germanium constituents on impurity concentration are studied based on Subband occupation by solving Boltzmann equation. The results show that electrons almost totally occupy the Δ2 valley when germanium constituent is up to 0.2, and the mobility with germanium constituent 0.4 is 64% higher than that of the unstrained silicon at low impurity concentration; and vertical channel is not so good for tensile stained Si devices. The model can also be used to calculate the electron mobility of other crystal face with an arbitrarily orientation if the parameters are correctly chosen, so the model offers some useful foundation for strained silicon devices and circuits.