In general, babies under 6 months of age do not need to be fed water for mixed feeding; babies over 6 months of age can be fed water, especially when the weather is dry and hot. Mixed feeding is a way of cross-feeding breast milk and formula milk. Formula milk should be prepared strictly according to the ratio of milk powder and water, which can fully satisfy the baby’s requirement for water, and babies under 6 months old do not need extra water feeding. 6-month-old babies began to add complementary foods, the digestion, absorption, metabolism of complementary foods need to consume water, this situation requires appropriate amount of water feeding, especially in dry weather, hot conditions, water loss is serious, timely hydration. Therefore, mixed feeding of infants under 6 months, do not need additional hydration, more than 6 months to add complementary foods, with the increase of complementary foods, moderate amount of water feeding.