Children’s legs are not straight mainly due to the following reasons: First, due to genetic factors, such as parents legs are not very straight, the child will be affected by genetic factors, so the legs will not be very straight. Second, due to the care of parents after birth, children after birth, parents often go to hold the child or carry the child to cause the legs often appear habitual action, can also lead to children’s legs are not straight. Third, due to early standing or walking, children’s bone development is not very perfect, within one year of age, too early to stand, standing for a long time or not to the age of one year too early to walk training will also lead to leg not straight. Fourth, due to vitamin D deficiency, resulting in X-shaped legs or O-shaped legs, etc., will also appear the phenomenon of legs not straight.