Abstract: To identify the optimum aging cycle for aged tobacco strips with high primary processing resistance and to investigate the correlations between the physical properties of tobacco leaves and the structure of cut tobacco, the penetrability of tobacco leaves was selected as the key physical property index for evaluating the primary processing resistance of tobacco strips. By optimizing the parameters of the penetrability detection method for aged tobacco strips, a method for evaluating the primary processing resistance was established. The variation patterns and degrees of penetrability of tobacco strips of different grades during aging were analyzed. The results showed that: 1) The penetrability of tobacco strip samples was extremely significantly positively correlated with the proportions of integral and long tobacco strands, while it was extremely significantly negatively correlated with the proportion of short tobacco strands (P < 0.01), indicating that the penetrability could be used as a key physical property index for evaluating the primary processing resistance of aged tobacco strips. 2) The parameters for measuring the penetrability of aged tobacco strips were determined. Under the premise of ensuring a 90% confidence interval on both sides, the minimum sample size was 64, with sample dimensions recommended to be (2-3) cm × (2-3) cm. 3) Within the aging period of 18-27 months, the tobacco sample grades in the order of the average decrease in penetrability of tobacco strip samples from three areas were B2F > C2F > C4F. The decrease in the penetrability of the samples of B2F and C2F grades reached a statistically significant level (P < 0.05) at the 27th month of aging, while the decrease in penetrability of the samples of C4F grade reached a statistically significant level (P < 0.05) at the 24th month of aging. 4) To improve the economic and control physical quality indexes of primary tobacco processing, the aged tobacco strips with lower penetrability, such as C4F, the primary processing should be carried out within 24 months of aging. For aged tobacco strips with higher penetrability, such as B2F, primary processing should be carried out within 27 months of aging.