To study the effects of infant formula supplemented with α-lactalbumin and tryptophan on brain development in newborn rats， this study used 30 SD rats at 7 days of age as experimental object， randomly divided into 3 groups， rat breast feeding group (ck)， the common infant formula feeding group and upgrade infant formula feeding， mixed feeding after 21 days. The effects of upgraded infant formula on brain development of newborn rats were investigated by measuring growth and development indexes， nerve function and intestinal microflora of rats. The results showed that upgrading infant formula could restore the abundance of intestinal flora at the genus level， significantly increased the content of beneficial bacteria AKK， and contributed to the establishment of a good intestinal flora. It could significantly increase the concentration of 5-HT and its metabolites in serum and diencephalon of rats， and promote neural development. Conclusions: Upgraded infant formula supplemented with α-lactalbumin and tryptophan could significantly increase the abundance of intestinal beneficial bacteria and the concentration of 5-HT and its metabolites in serum and diencephalon tissues of newborn rats， with potential health benefits for intestinal and neural development. This study could provide theoretical basis and scientific support for the upgrading of infant formula milk powder.