If your 7-month-old baby can’t sit still, the cause may be due to prematurity, calcium deficiency or backward development, you can continue to observe and give him/her assisted training, calcium supplementation and rehabilitation training. 1. Some premature babies need to be corrected for their age in order to determine whether they are behind in growth and development. For example, if a baby born at 36 weeks is 7 months old, the corrected gestational age should be 6 months, and if the baby can’t sit at 7 months old, he/she is not backward and can be assisted in training. 2. In infants with calcium deficiency, the bones become soft, the muscles will be flaccid, can not maintain the normal muscle tone when sitting, should be based on the calcium of the specific supplement, eat more calcium-rich foods (such as marine fish, lean meat, etc.), more sunshine, in order to promote the absorption of calcium. 3. If the full-term baby will not sit 7 months after birth, relative to 1 month behind, need to observe its head up, turn over the month whether the same behind children of the same age, if the overall development of backwardness need to go to the neurology department to find out the cause of the rehabilitation training in a timely manner. 7 months baby can not sit steadily need to identify the cause, timely specialist consultation, early detection and early treatment, so as not to delay the condition.