The causes of lower lip trembling when children cry include the following: first, caused by children crying more intensely. Some children are very short-tempered and are particularly violent when they cry, and children will have a lower lip tremble when they cry. Children can be soothed appropriately so that they have fewer opportunities to lose their temper. Secondly, children with cerebral palsy have symptoms. If the child has cerebral palsy, it will cause abnormal muscle tone, and the child will also have obvious trembling of the lower lip when crying, scissor gait, and very high muscle tone in the lower limbs. The lower lip tremor will be relieved after the child’s muscle tone is restored through timely rehabilitation.