Abstract: 【Objective】 This project aims to investigate the differences in milk composition between the two periods and the potential regulatory mechanisms by analysing the milk composition and plasma metabolome of Ili horses during colostrum and regular milk. 【Methods】 Milk and blood samples were collected from eight Yilihorses on day 0 and day 30 of parturition, respectively, and milk routine analyses of milk from the two periods were carried out by a milk composition analyser, and comparative analyses of plasma metabolites were performed by non-targeted metabolomics. 【Results】 The results revealed that milk fat, milk protein, solids and non-solids were significantly higherin colostrum than in regular milk (P<0.05), and lactose was significantly lower in colostrum than in regular milk (P<0.05). Plasma metabolites were analyzed and a total of 363 differential metabolites were screened according to conditions. 【Conclusion】 Pathway enrichment analysis of differential metabolites significantly enriched a total of 5 functional pathways. The presence of many metabolites in plasma during colostrum period was associated with the promotion of fatty acid metabolism, glucose metabolism, and amino acid metabolism in the mammary gland, such as palmitic acid, D-threitol, biotin, and pantothenic acid.