This study aimed to determine the critical stage of fat deposition in Shaziling pigs and to identify key candidate genes and regulatory pathways associated with lipid metabolism. A total of 60 Shaziling pigs were slaughtered at 60d, 90d, 120d, and 180d. Growth performence, carcass traits, adipocyte morphology, fatty acid composition, and transcriptomic profiles of backfat tissue were analyzed to characterize phenotypic and molecular changes during fat deposition. The period between 90d and 120d represents a critical stage of accelerated fat deposition in Shaziling pigs, accompanied by significant increases in fat percentage, adipocyte area, and alterations in fatty acid profiles(P<0.05). Gene expression analysis revealed significant alterations in key adipogenic regulators, including CCAAT/enhancer-binding protein alpha (C/EBPα), fatty acid synthase (FAS), acetyl-CoA carboxylase (ACC), Forkhead Box O1 (FOXO1) and sterol regulatory element-binding protein 1c (SREBP-1c) (P<0.05). Transcriptomic analysis identified 362 differentially expressed genes (DEGs) between 90d and 120d, with 106 DEGs enriched in lipid metabolism-related pathways, such as Tumor necrosis factor-alpha (TNF-α), Phosphoinositide 3-kinase–protein kinase B (PI3K–Akt), Peroxisome proliferator-activated Receptor (PPAR), Nuclear factor kappa-light- chain-enhancer of activated B cells (NF-κB), and FOXO signaling pathways.Integration of protein interaction and co-expression networks highlighted FBJ murine osteosarcoma viral oncogene homolog (FOS), Jun proto-oncogene (JUN), Jun B proto-oncogene (JUNB), Bone morphogenetic protein 6 (BMP6), Suppressor of cytokine signaling 3 (SOCS3), and Interleukin 6 (IL6) as candidate regulators significantly associated with carcass fat percentage and backfat thickness. These findings demonstrate that 90–120d is a pivotal stage for fat deposition in Shaziling pigs and reveal candidate genes and pathways involved in lipid metabolism. The results provide new insights into the genetic regulation of lipid metabolism in IPBs and offer potential targets for improving meat quality and nutritional value.