The sandstone reservoir in the deep series of strata in Anpeng area is considered as ultra-low porosity and permeability reservoir with nanometer and micrometer pores,the regularity of reservoir physic properties is poor, the flow characteristics of the fluid are complex, and the classification and evaluation of the reservoir are difficult. Nuclear magnetic resonance measurements were performed on the saturated water cores. By comparing the T2 spectrum with mercury intrusion curve, the conversion coefficients of T2 relaxation time and throat radius were obtained by the least squares method and the pore-throat size distributions of cores were obtained. Based on NMR T2 distribution and fractal theory, the fractal dimension of pore-throat is calculated and the relationship between pore-throat parameters and permeability is analyzed. The results show that the pore-throat size distributions show bimodal characteristics, compared with the distribution of pore-throat size obtained by mercury intrusion, the NMR measurements can obtain the pore structure more comprehensively. The pore-throat radius is mainly distributed in the range of 0.1-10μm and range of 0.001-0.1μm when the permeability is more than 1×10-3μm2 and less than 1×10-3μm2 respectively. NMR T2 distribution shows fractal characteristics in a certain T2 interval, and the fractal dimension, the mainstream throat radius, the average pore-throat radius and the median radius are all related to the permeability of the reservoir in the form of a power function.