The purposes of this study were to understand the body weight changes of bottle -or breast-fed neonates from birth to one week and at the age of one month. 53 fully-bottle-fed neonates and 39 fully-breast-fed neonates were involved in this study. The results were identified as: (1) The bottle-fed neonates significantly lost weight. (2.95% of physiological body weight loss) on day 2 after birth, and regained weight on day 3 (2) The breast-fed neonates significantly lost weight (about 4.16% of physiological body weight loss) at the age of 2 days and 3 days, and regained weight on the fourth day after birth; (3) Although the breast-fed neonates had more physiological body weight loss than the bottle-fed neonates during their first week, they regained more weight on day 6 (p<0.01). At one month after delivery, there were no significant difference in body weight between these two groups.