In this paper, the mechanism of enhanced oil recovery using lipophobic and hydrophilic polysilicon (LHP) nanoparticles ranging in size from 10 to 500 nm for changing the wettability of porous media was analysed theoretically. A one-dimensional two-phase mathematical model considering the migration and adsorption of LHP and wettability change in reservoir rock was proposed, and a simulator was developed to quantitatively predict the changes in relative and ef- fective permeability of the oil and water phases and the oil recovery in sandstone after water driving. Numerical simula- tions were conducted to study the distribution of the particle concentration, the reduction in porosity and absolute per- meability, the LHP volume retention on pore walls and in pore throats along a dimensionless distance, and oil production performance. In conclusion, oil recovery can obviously be improved by flooding with hydrophilic nanometer powders though permeability declines for the retention of nanoparticles in porous media. It is suggested that an LHP concentration ranging from 0.02 to 0.03 is preferable to enhance oil recovery. In this paper, the mechanism of enhanced oil recovery using lipophobic and hydrophilic polysilicon (LHP) nanoparticles ranging in size from 10 to 500 nm for changing the wettability of porous media was analytically theoretically. A one-dimensional two-phase mathematical model considering the migration and adsorption of LHP and wettability change in reservoir rock was proposed, and a simulator was developed to quantitatively predict the changes in relative and ef- fective permeability of the oil and water phases and the oil recovery in sandstone after water driving. Numerical simula- tions were conducted to study the distribution of the particle concentration, the reduction in porosity and absolute per-meability, the LHP volume retention on pore walls and in pore throats along a dimensionless distance, and oil production performance. improved by flooding with hydrophilic nanometer powders though permeability declines for the retention of nanopar It is suggested that an LHP concentration ranging from 0.02 to 0.03 is preferable to enhance oil recovery.