Specificity protein 1 (SP1) is a ubiquitous transcription factor that plays an important role in controlling gene expression. Although important in mediating the function of various hormones, the role of SP1 in regulating milk fat formation remains unknown. To investigate the sequence and expression information, as well as its role in modulating lipid metabolism, we cloned SP1 gene from mammary gland of Xinong Saanen dairy goat. The full-length cDNA of the SP1 gene is 4376 bp including 103 bp of 5'UTR, 2358 bp of ORF (HM_236311) and 1915 bp of 3'UTR, which is predicted to encode a 786 amino acids polypeptide. Phylogenetic tree analysis showed that goat SP1 has the closest relationship with sheep, followed by bovines (bos taurus, odobenus and ceratotherium), pig, primates (pongo, gorilla, macaca and papio) and murine (rattus and mus), while the furthest relationship was with canis and otolemur. Expression was predominant in the lungs, small intestine, muscle, spleen, mammary gland and subcutaneous fat. There were no significant expression level differences between the mammary gland tissues collected at lactation and dry-off period. Overexpression of SP1 in goat mammary epithelial cells (GMECs) led to higher mRNA expression level of peroxisome proliferator-activated receptor-gamma (PPAR gamma) and lower liver X receptor alpha (LXR alpha) mRNA level, both of which were crucial in regulating fatty acid metabolism, and correspondingly altered the expression of their downstream genes in GMECs. These results were further enhanced by the silencing of SP1. These findings suggest that SP1 may play an important role in fatty acid metabolism.