The baby’s body is soft, also known as muscle strength and hypotonia, commonly seen in the following cases: 1, genetic metabolic disease or chromosomal disorders caused by, such as congenital hypothyroidism or trisomy 21, as well as certain gene fragments of the deletion, duplication, etc. can appear muscle strength and hypotonia, motor development is delayed, accompanied by mental retardation, need to promptly go to the hospital to give the necessary examination to clear diagnosis. 2, brain injury syndrome, mostly due to the existence of high-risk factors during the perinatal period, resulting in abnormal development of brain function and low muscle strength and tone, such as still unstable vertical head at 3-4 months of age, and hands still no active grasping awareness at 5 months of age. 3, spinal cord lesions, such as spinal cord tumors, can easily lead to trunk trunk softness, but normal intellectual development. Whichever the cause is, the patient needs to be seen by a hospital promptly.