This study aimed to analyze the phenotypic diversity of sesame germplasm in Jiangxi province， China， and construct a reliable core germplasm population， providing theoretical basis and reference for promoting the efficient utilization of sesame germplasm. We used 736 sesame germplasms from various counties and cities in Jiangxi province as experimental materials， and conducted diversity analysis on 24 phenotypic traits. Three sampling methods， six sampling ratios and eight clustering methods were employed to identify optimal solution for constructing the primary core germplasm. We performed mean T-test and variance F-test on multiple parameters of the original germplasm and core germplasm， and compared the eigenvalues， contribution rates， and cumulative contribution rates of the two populations through principal component analysis. In addition， we obtained genotype data for 64 germplasms and 16 core germplasms of Ji′an using 12 pairs of polymorphic markers， followed by polymorphism analysis， evaluation， and genetic similarity analysis. The 736 local sesame germplasms in Jiangxi province exhibited rich genetic diversity. The genetic diversity index of phenotypic traits ranged from 0.5129 to 2.0833， with a variation range of 4.83% to 41.52%. The genetic diversity index of quantitative traits （1.7140 to 2.0833） was generally higher than that of qualitative traits （0.5129 to 1.1054）. The 110 core germplasm constructed using the “multiple clustering priority sampling method + 15% sampling ratio + variable class average method + Euclidean distance” effectively represented the diversity of the original collection. The cumulative contribution rates of the original collection and core collection were 80.533% and 82.631%， respectively， indicating that the core collection could explain over 80% of the genetic information. Molecular analysis of the sample showed， 96.25% of the polymorphic loci in 16 core germplasms were in included in 64 original germplasms， both were essentially similar on polymorphisms， with no significant difference in the mean T-test （except for the number of observed alleles）. The genetic similarity between the two collections was also essentially similar. The 16 mini-core germplasms could preliminarily represent the genetic diversity of the 64 Ji′an sesame germplasms. Collectively， these results indicated that the 110 core germplasm collection could represent the genetic diversity of the 736 Jiangxi sesame germplasms to a significant extent for preservation and utilization.