Abstract: According to the physical property of the reservoir in Henan Oilfield and the poor effect of profile control,the initial particle size of polymer nano-microsphere was optimized based on the expansion volume of polymer nano-microsphere and reservoir characteristics.Through flowing test of the core,the plugging rate in single sand pipe and the EOR after injecting polymer nanoparticles were studied in high and low permeability parallel sand pipes.The results showed that plugging rate of the polymer nanoparticles in the sand pipe reached 80.5%,and different areas had different fluctuating pressure after water flooding with the polymer nanoparticles.This indicates that migration,plugging,elastic deformation,re-migration and re-plugging occurred with the polymer nanoparticles in sand pipe.Polymer microspheres entered and blocked the hypertonic pipe first,and then changed the heterogeneity of parallel sand pipe,finally,crude oil in low permeability was driven.During the process,the oil recovery ratio of the high permeability sand pipe improved 20.5%.The field application in Well C9 showed that,after polymer nanoparticle flooding in injection well,the injection pressure increased,water injection profile significantly changed,and the corresponding oil well production increased.The test indicates that deep profile control with polymer nanoparticle is suitable for Henan Oilfield.This technology can realize deep profile control,increase swept volume and enhance oil recovery.