The startle reflex in newborns is a normal physiological phenomenon that does not affect the development of the brain or intelligence and usually disappears in about 3-4 months. Newborn startle reflex refers to the involuntary shaking of newborns, which is mostly caused by the immature development of the cerebral cortex, the incomplete nervous system and the high excitability of central nerve cells. When the startle reflex occurs, the infant’s whole body shakes involuntarily for a short time and sometimes cries out loud, but it can soon be relieved on its own or with parental reassurance. As the infant grows older and the central nervous system matures, it usually disappears in 3-4 months and parents need not worry too much. Therefore, parents can soothe their newborns when they have a startled jump to increase their sense of security. If the startle still occurs after 4-5 months, it is recommended that the infant be examined by a pediatrician in a hospital in case the startle is undetected due to calcium deficiency or other causes, thus delaying treatment.