A 2-year-old child who can’t jump on both feet may have a poorly developed brain, but it can’t be ruled out as a normal condition or caused by weakness of both lower limbs. 1. Normal situation: if the child is relatively small, like to protect themselves, do not dare to try new actions, may appear 2 years old will not jump on both feet. 2. Poor brain development: If the child’s brain is underdeveloped, there may be sensory integration disorders, poor balance and coordination of the body, which may result in the child not being able to jump on both feet at the age of two. The child may also have clumsy movements and slurred speech. 3. Double lower limb weakness: when the child has double lower limb muscle strength is low, can not well control and support the body, there will be 2-year-old can not jump on both feet. If the child is not able to jump at the age of 2, it is recommended to consult a doctor in a timely manner, under the guidance of the doctor, to improve the relevant examination, to clarify the cause of the disease, and to carry out regular treatment as soon as possible.