The neck of a three-month-old baby is still very soft, indicating low muscle tone, which may be caused by physiological or pathological factors, such as the baby’s lack of cooperation during the physical examination; pathological factors such as various myopathies. Muscle tone is the force generated by muscle cells pulling on each other. The tension of a muscle in a resting, relaxed state is called muscle tone. Baby neck muscle tone is low, can be caused by a variety of myopathies, peripheral neuropathy, myasthenia gravis, radiculitis or cerebellar damage, etc., the spinal cord conduction of proprioception of the blockage of nerve fibers can also make the muscle tone decreased, part of the extrapyramidal injury can also lead to a decrease in muscle tone. Three months of the baby’s neck is still very soft, there may be other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.