Due to small pores，smaller throat，and lower mobility of crude oil in Jilin low permeability tight reservoir，water drive effect is poor. A nano fluid enhanced permeability and oil displacement（NFEPOD）system was adopted，and through the core oil displacement experiment the oil displacement efficiency of the NFEPOD system on the tight core was investigated，through the core nuclear magnetic resonance test and CT scanning，the influence of the pore structure of the tight reservoir on the oil displacement effect of nano fluid was focused on. The results showed that the NFEPOD system could reduce the injection pressure of tight core oil displacement experiment，with a maximum decrease of 46.2%. When the pore structure of tight reservoir was good，the oil displacement effect was obvious，with a maximum increase of 30.21%. The NFEPOD system could remarkably enhanced oil recovery when the crude oil was distributed in pore throat with an average pore radius greater than 1 μm. CT scanning of cores showed that the average pore throat radius，effective connected pore ratio and pore coordination number of tight cores would affect the injection pressure and oil displacement efficiency of the NFEPOD system，the average pore throat radius and the proportion of effectively connected pores had a greater impact.