Abstract: A non-destructive and non-invasive method for analyzing the nanopore structure of tobacco leaves was proposed using cryogenic freeze-thaw nuclear magnetic resonance technology, combined with the Gibbs-Thomson effect to determine the relationship between the liquid freezing point temperature and the pore size of the liquid. Taking B2F upper part, C2F middle part, and X2F lower part of Yunnan tobacco leaves before and after drying as the objects, the relationship between tobacco leaf parts, drying methods and the distribution of nanopores in tobacco leaves was analyzed and studied. As shown by the results, the nuclear magnetic resonance signal intensity was highly linearly correlated with the moisture content in the sample, with fitting linear coefficients higher than 0.99. The nuclear magnetic resonance signal intensity of the sample could directly reflect the moisture content and volume in tobacco samples. The pore size of nanopores in tobacco leaves was relatively small and unevenly distributed, with about 90% of the pore size within 1.9, 20.6 nm. The proportion of pores (4.6, 8.6 nm in the upper and middle parts of tobacco leaves was significantly lower than that in the lower part of tobacco leaves, while the proportion of pores in the (10.6, 20.6 nm was significantly higher. Compared with the lower part of tobacco leaves, the pore structure was looser, and the differences in pore structure may be mainly influenced by factors such as tobacco leaf location, light, nutrition, and moisture. After drying, the nanopore structure of tobacco leaves underwent significant changes, increasing the proportion of smaller pore sizes and decreasing the proportion of larger pore sizes by both heated stream drying and drum drying.