Floating thumb is a congenital hand deformity that is a type IV thumb dysplasia where the thumb has no metacarpal bone and hangs from the hand like a ball of flesh that only swings with the palm of the hand. Such a thumb will not improve without surgical correction. The most traditional treatment option for floating thumb is to show finger thumbing, where the floating thumb is directly removed and the index finger is moved to the thumb position to be used as a thumb, after surgery the child will always have only four fingers, which is a great pity. Later on, the treatment of floating thumb is based on the preservation of the fifth finger, using the method of metatarsal reconstruction, taking part of the metatarsal bone from the child’s foot to reconstruct the first metacarpal bone, after the operation, the thumb not only has the shape but also the function. However, the surgery has a certain chance of bone resorption and necrosis, and the bone is taken from the foot, which will more or less have some impact, so some parents are very concerned about this point. Nowadays, we use the hemimacral bone graft reconstruction technique to treat floating thumb, which is another treatment option to preserve the five fingers after metatarsal reconstruction. The bone is taken from the second metacarpal bone of the affected hand to reconstruct the first metacarpal bone, which greatly reduces the chance of bone resorption and necrosis, and the operation is performed on the hand only, without touching other parts of the child’s body. The surgery is divided into two phases. The first phase moves the bone, and the second surgery is done once the bone heals to establish the function of the thumb so that the thumb can do something. With diligent exercise, the shape and function of the thumb will improve greatly.