Abstract: The solution characteristics and oil displacement effect of a nano-silica modified polymer with nanoparticle-polymer composites were evaluated to enhance the applicability of oil displacement polymers in reservoirs and further improve oil recovery. The performance differences between different polymer solutions, including a nano-silica modified polymer and two unmodified polymers, were evaluated by Brookfield viscometer and HTHP Anton Paar rheometer at 90 °C and 20,000 mg/L of salinity. The oil displacement effects of above polymers were analyzed by core flooding experiments. The distributions of crude oil in the pore model before and after flooding with three kinds of polymers were observed through micro oil flooding experiments. The experimental results showed that the molecular network had better performance in deformation recovery because the interaction between the molecules of nano-silica modified polymer was stronger. Compared with the other two polymers, the nano-silica modified polymer presented large improvement in increasing viscosity, improving temperature resistance, salt resistance, enhancing shearing endurance and aging stability, and increased the oil recovery ratio by 21 percentage points, which was greater than that of branched polymer (13 percentage points) and that of linear polymer (9 percentage points) respectively. So, the nano-silica modified polymer can effectively alleviate the heterogeneity of porous media, greatly reduce the number of island-like oil beads and long strip-like remaining oil in the porous media, and significantly decrease the saturation of residual oil.