【Objective】 To provide scientific references for germplasm conservation and development and utilization of Castanopsis carlesii, the geographical variations of seed morphological characteristics and nutrient content of C. carlesii from different provenances were analyzed. 【Method】 Seeds of C. carlesii were collected from 357 individuals growing in natural distribution areas of thirteen provenances. Six morphological characteristics (seed length, seed width, length width ratio, volume, surface area and 1 000-seed weight) and nutrients (soluble sugar and starch) of seeds were measured, and then variance, correlation and cluster analyses were conducted.【Result】 Seeds’ morphological characteristics were significantly different between and within provenances (P < 0.01); the mean values of seed length, width, length width ratio, volume, surface area and 1 000-seed weight ranged from 0.93-1.02 cm, 0.82-0.93 cm, 1.07-1.21, 0.32-0.46 cm³, 1.83-2.32 cm² and 397.15-599.67 g, respectively. The nest analysis of variances showed that the maxima of seed length, width, volume, surface area, and 1 000-seed weight were observed in seeds from Jiangxi Dingnan (JXDN), and significantly differed from those from other provenances. The 1 000-seed weight of Anhui Qimen (AHQM) was 66.23% that of JXDN, and the seed length, width, volume and surface area were comparatively smaller. The percentages of starch and soluble sugar were 31.80% and 21.76%, respectively. The nutrient contents of C. carlesii were significantly different between provenances (P < 0.01); the coefficients of variation were 14.06% and 30.62%. The average coefficient of phenotypic differentiation was 28.15%, and genetic variation within provenances was the main source of the genetic variation of morphology characteristics. The correlation analysis showed that starch and 1 000-seed weight had the most positive correlations with seed width (P < 0.05), while sugar had an extremely significant correlation with seed length and length-width ratios (P < 0.01). Seed length showed a significant negative correlation with longitude (P < 0.05). The length-width ratio showed an extremely significant negative correlation to longitude (P < 0.01), and had significant negative correlation with precipitation during the coldest quarter (P < 0.05). The starch showed a significant correlation to annual mean temperature. The cluster analysis showed that the thirteen provenances could be divided into three groups. Group Ⅰ included JXDN, which possessed large sized seeds, high soluble sugar and high starch. Group Ⅱ included AHQM, Jiangxi Xinfeng (JXXF), Zhejiang Kaihua (ZJKH) and Guangdong Lianping (GDLP), which had small sized seeds, high soluble sugar and low starch groups; the other eight provenances fell into group Ⅲ, exhibiting medium sized seeds, and medium soluble sugar and starch contents. Adjacent provenances did not cluster together preferentially, indicating that there is no obvious geographical variation of C. carlesii.【Conclusion】 The phenotypic diversity of C. carlesii was the result of genetic and environmental factors. In addition, the variation in seeds was mainly influenced by longitude, annual mean temperature, and precipitation of the coldest quarter. The genetic variation within provenances was the main source of genetic variations of seed characteristics; therefore, the selection and utilization of superior individual plants should be strengthened in the genetic improvement of C. carlesii. JXDN has the characteristics of large seeds and high nutrition, and offers the potential for excellent provenances.