ABSTRACT: [Background] DNA methylation plays a crucial role in regulating cell proliferation, differentiation, gene expression, and embryonic development. However, the comprehensive changes in genome-wide DNA methylation during early pregnancy in sows remain unknown. This study aimed to investigate the DNA methylation profiles and to construct an early gene pool of sows during early gestation.[Results] In this investigation, we utilized blood samples from 20 healthy sows and applied Reduced Representation Bisulfite Sequencing (RBSS) technology to systematically examine alterations in DNA methylation in sow blood during early pregnancy. Screening and validating the Methylation differential genes by using bisulfite sequencing PCR (BSP) and Quantitative Real-time PCR (RT-qPCR). Our findings indicated a significant increase in methylation levels on day 28 of pregnancy (pre28) compared to non-pregnancy (ctrl) across various gene elements, including CGI, promoter, and genebody. A total of 64,908 differentially methylated sites (DMCs) and 12,119 differentially methylated regions (DMRs) were identified, predominantly exhibiting methylation upregulation. Randomly selected five differentially methylated genes—VBP1, UPRT (upregulated methylation), RPL10, RAB33A, and CD93 (downregulated methylation)—were validated. Between the pregnant (pre28) and non-pregnant (ctrl) groups the BSP results showed highly significant methylation differences (P<0.01) in VBP1, UPRT, RPL10, and RAB33A. DMC gene ontology (GO) analysis revealed significant enrichment in nuclear receptor activity, negative regulation of cysteine-type endopeptidase activity during apoptosis, heme binding, and hormonal activity. DMRs GO analysis highlighted significant enrichment in 1-acylglycerol-3-phosphate O-acyltransferase activity, regulation of transforming growth factor β receptor signaling pathway, mitochondrial outer membrane and myotubular cell development, and cellular calcium homeostasis. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis demonstrated significant enrichment in the MAPK signaling pathway and the PI3K-Akt signaling pathway.[Conclusion] During sow early gestation, DNA methylation is significant changes and is mainly upregulated. The observed upregulation of DNA methylation during early gestation in sows may regulate the MAPK and PI3K-Akt signaling pathways, potentially influencing embryonic development. Methylated differential genes VBP1 and RPL10 can be used as potential markers for early sow pregnancy diagnosis. These findings offer novel insights into the epigenetic changes occurring in sows during early gestation.