The standard weight for a four-month-old baby is 6.9-9.2kg for boys and 6.34-8.47kg for girls. According to China’s weight percentile table for children and adolescents aged 0-18, there are some differences between boys and girls, and the normal weight range for a four-month-old boy is 6.9-9.2kg, and for a girl is 6.34-8.47kg. The standard weight can be used as a reference, each child’s genetic background, nutritional status is different, there will be differences in weight, you can observe the child’s weight and the standard range of comparison to determine the child’s development, if light or heavy more than two standard deviations need to pay attention to, and consult a doctor in a timely manner. Parents are advised to measure their children’s weight and height on a regular basis and draw growth charts.