Water injection development in low permeability reservoir generally results in serious channeling of injected water and a large amount of remaining oil. Polymer microspheres and low salinity water are proven effective approaches for profile control and oil displacement in hydrocarbon reservoirs. The former focuses on profile control while the latter favors oil displacement，and thus their combination is expected to achieve the dual effect of profile control and oil displacement. This paper evaluated the effects of simultaneously injecting nano-polymer microspheres and low salinity water via core floods. Nuclear magnetic resonance T₂ spectrum and imaging test were used to reveal the extent of residual oil in pores of various sizes during core flooding as well as the mechanism of oil displacement. The results showed that the microspheres could eliminate water channeling and change flow direction，forcing the low salinity water to enter smaller pores and improving the sweep and oil displacement efficiency. The lower the salinity，the higher the produced oil from small and medium-sized pores. Increasing the concentration of microspheres and decreasing the salinity of injected fluid could enhance the plugging effect of microspheres，resulting in enhanced injection pressure and oil recovery. This study confirmed the potential of synergistic flooding with low salinity water and nano-polymer microspheres in improving oil recovery in low permeability reservoirs.