A suspension of nanoscale polysilicon particles (NSPP) is injected into low permeable sand formations for reducing flow resistance of water. A set of instruments was assembled to get insights into the characteristics, adsorption and transport of the NSPP, wettability alteration, and its effects on two-phase flow performances in porous media. The TEM images show that the particles are approximate spheres with diameters from 10 to 200nm. The NSPP could be adsorbed on the pore surfaces, and it looks like frost on the grains in the crossing section of sandstone. The wetting angle of water drop becomes far larger than 90o after the adsorption of the NSPP. It implies that the adsorption on pore surfaces leads to wettability alteration from water-wetness to oil-wetness. Wettability alteration is a major factor to change the percolation flow resistances of two phases, which has been verified by the change in relative permeabilities of the two phases. The flowable improvement of water results from the reduction in filtrational resistance of water in the sand formation.