Background and Objectives: Understanding human milk composition is critical for setting nutrient recommend- ed intakes (RNIs) for both infants and lactating women. However, nationwide human milk composition remains unavailable in China. Methods and Study Design: Through cross-sectional study, human milk samples from 11 provinces in China were collected and their compositions were analyzed. Nutritional and health status of the lac- tating women and their infants were evaluated through questionnaire, physical examination and biochemical indi- cators. Results: A total of 6,481 breast milk samples including colostrum (1,859), transitional milk (1,235) and mature milk (3,387) were collected. Contents of protein, fat, lactose, total solid and energy of more than 4,500 samples were analyzed using a human milk analyzer. About 2,000 samples were randomly selected for 24 mineral analyses. Free B-vitamins including thiamin, riboflavin, pyridoxal, pyridomine, pyridoxamine, nicotinamide, nic- otinic acid, flavin adenine dinucleotide (FAD), biotin and pantothenic acid were analyzed in 1,800 samples. Ami- no acids (~800) and proteins (alpha-lactoalbumin, beta-casein, and lactoferrin) were analyzed. In addition, serum retinol and carotenoids, 25(OH)D, vitamin B-12, folic acid, ferritin and biochemical indicators (n=1,200 to 2,000) were analysed in the lactating women who provided the breast milk. Ongoing work: Fatty acids (C4-C24), fat- soluble vitamins and carotenoids, are on-going analysis. Conclusions: A regional breast milk compositional da- tabase is at an advanced stage of development in China with the intention that it be available on-line.