Background: Optimal nutrition for lactating mothers is importance for mother and infants' health and well-being. We determined the nutrient intake and dietary changes during the first 3-month of lactation, and its potential effect on health and disease risk.Method: Personal interviews were conducted to collect a 24h diet recall questionnaire from 199 healthy lactating women in the postpartum days 2, 7, 30, 90 and healthy 58 non-pregnant women served as the controls.Results: We found in lactating women (1) the mean daily energy and carbohydrate intake was lower than that of the Chinese Recommended Nutrient Intake (RNI, 2600 Kcal, 357.5 ~ 422.5g) by 11% ~ 17% and 33% ~ 49%, respectively; (2) the fat intake increased from 3% to 13%, which was 9 ~ 77% higher than the RNI (57 ~ 86.7g); (3) the protein intake exceeded the RNI of 85g by 32 ~ 53%; (4) the total calories consumed from carbohydrate (39%-44%), fat (34% ~ 42%) and protein (20%-23%) failed to meet Chinese RNI (5) the intake of vitamin C, B1, folate, zinc, dietary fiber, and calcium was 5% ~ 73% lower than the RNI while vitamin B 2, B 3, E, iron and selenium intake was 20% to 3 times higher than the RNI. Nutrient intake in the control group was lower for all nutrients than the recommended RNI.Conclusion: Lactating women on a self-selected diet did not meet the Chinese RNI for many important micronutrients, which may influence the nutritional composition of breast milk and thus impact the potential health of mothers and infants. RNI should consider the regional dietary habits and culture. A single national RNI is not applicable for all of China. Nutritional education into the community is needed.