It is often occured that the diarrhea of newborn caused by the malabsorption and intolerance of lactose. In order to research the relation of the malabsorption and intolerance of lbactose and the diarrhea of newborn, we mehsured stool lactose levels in 142 cases. The results showed that 60 cases were positive (the incidence rate waw 42. 3%). It suggested that the malabsorption and intolerance of lactose may be an inpostant cause of the diarrhea of nweborn We divided these patients into two groups at random. Exclusion of lactose dietotherapy was adopted in the experimented group, the effective rate was 96. 7%, no side-effect; on the contrary, the effective rate of the control group (exclusion of the lactose dietotherapy was not adopted) was 40%. The difference between the two groups was statisically significant, (P＜0.001 ). We concluded that if there is patient of mabosorption and intolerance of lactose, we must take exclusion of lactose dietotherapy. It is often occured that the diarrhea of ​​newborn caused by the malabsorption and intolerance of lactose. In order to research the relation of the malabsorption and intolerance of lbactose and the diarrhea of ​​newborn, we mehsured stool lactose levels in 142 cases. 60 例 were positive (the incidence rate waw 42. 3%). It suggested that the malabsorption and intolerance of lactose may be an inpostant cause of the diarrhea of ​​nweborn We divided these patients into two groups at random. Exclusion of lactose dietotherapy was adopted in the experimented group, the effective rate was 96. 7%, no side-effect; on the contrary, the effective rate of the control group (exclusion of the lactose dietotherapy was not adopted) was 40%. The difference between the two groups We were that if there is patient of mabosorption and intolerance of lactose, we must take exclusion of lactose dietotherapy.