Abstract: Using NMR 2-D spectrum and online testing technology, Core oil saturation analysis by nuclear magnetic resonance diffusion-relaxation spectrum was established.On-line NMR tests of water displacement at different velocities in cores of different intervals of different Wells were carried out. By comparing the area values and distribution characteristics of NMR T₂ spectrum tested at different times, the degree of oil recovery in different pore intervals was calculated. The contribution rate of different pores to recovery degree, water displacement effect and residual oil distribution in core were analyzed and evaluated. The large and medium pores in the experimental core of TK150 well reservoir section contribute greatly to the recovery degree, The large, medium and small pores in the experimental core of weak water section contribute greatly to the recovery degree. However, large pores account for a small proportion of total pores, so the recovery degree is lower than that of reservoir cores. The large and medium pores in the experimental core of TK960 well reservoir section contribute greatly to the recovery degree, The medium and small pores in the experimental core of medium water section contribute greatly to the recovery degree, The large and medium pores in the experimental core of strong water section contribute greatly to the recovery degree Residual oil is distributed in pores at all scales after core water displacement in different intervals of different Wells.