Numerical simulation study on electron mobility in independent DG MOSFETs with back gate biased in accumulation, flatband and inversion operation regions is presented in this paper. A numerical simulation program of the electron transport in the independent DG MOSFETs, which includes both phonon and surface roughness scattering mechanisms, is developed. From it, the dependence characteristics of the DG MOSFET electron mobility on the device operation conditions and the structure parameters are discussed. It is shown that DG MOSFET exhibits higher mobility when back gate is biased in inversion region compared to simulation results when back gate is in flat-band or accumulation regions. Mobility enhancement is observed in devices with thinner silicon film, when higher field is applied, which can be attributed to ??volume inversion?? in DG MOSFET.