A total of 2 676 blood samples from four local pig breeds in Hunan Province(452 Xiangxi Black Pigs, 1 427 Ningxiang Pigs, 451 Qianshao Spotted Pigs, and 346 Daweizi Pigs) were collected during seed industry monitoring from 2023 to 2024. Genotyping was performed using the GGP 50K SNP array. Purebred individuals were screened out through the animal genome breed composition method, and then the genetic diversity, bloodline purity, kinship and family structure of the fourlocal pig breeds in Hunan were analyzed based on the screened purebred individuals. The results showed that the polymorphic information content(PIC) of the Ningxiang Pig population was 0.251, the average observed heterozygosity(Ho) was 0.245, the average expected heterozygosity(He) was 0.251, and the average continuous homozygous fragment(ROH) length(LROH) was 5 166.733 kb. The inbreeding number(FROH) calculated based on the ROH fragment was 0.002 2, and the minimum allele frequency(MAF) was 0.185. The PIC of the Qianshao Spotted Pig population was 0.281, Ho was 0.285, He was 0.281, LROH was 5 706.452 kb, FROH was 0.002 5, and MAF was 0.207. The PIC, Ho and He of the Daweizi Pig population were all 0.239, the LROH was 4 769.535 kb, the FROH was 0.002 1, and the MAF was 0.177. The PIC of the Xiangxi Black Pig population was 0.390, Ho was 0.343, He was 0.390, LROH was 5 201.896 kb, FROH was 0.002 3, and MAF was 0.299. Considering all genetic diversity metrics, the Xiangxi Black Pig showed the highest genetic diversity, whereas the Daweizi Pig exhibited relatively lower diversity. Except for the Qianshao Spotted Pig, the other three breeds showed well-maintained lineage purity with few admixed individuals and a good conservation situation. Principal component analysis revealed clear genetic separation among the four breeds. Among them, the Xiangxi Black Pig formed two relatively independent subclusters, suggesting internal subpopulation differentiation and the farthest from other breeds, and the most unique genetic background. The Daweizi Pig clustered independently and compactly, indicating a secondary genetic uniqueness. The Ningxiang Pig and Qianshao Spotted Pig partially overlapped, reflecting a close genetic relationship while retaining distinct core clusters, which suggested that while sharing a certain genetic background, they had also accumulated specific variations of the breeds. Phylogenetic analysis(NJ tree) showed preferential clustering by breed, with the Xiangxi Black Pig and Daweizi Pig forming independent branches, whereas the Ningxiang Pig and Qianshao Spotted Pig were genetically closer. When the ancestral component number(K) was assumed to be 2, the uniqueness of the Daweizi Pig was revealed. When K=3, Xiangxi Black pig was classified as an independent component. The Ningxiang Pig and the Qianshao Spotted Pig were not completely distinguished until K=4, which indicated a relatively close genetic relationship and a relatively complex history of genetic mixing between the two breeds. Furthermore, within-breed NJ tree analysis indicated multiple family lineages in each breed(10 for Ningxiang Pig, 8 for Xiangxi Black Pig, 9 for Daweizi Pig, and 7 for Qianshao Spotted Pig), demonstrating substantial genetic variation maintained at the family level.