A patient consulted me, saying that his baby was already one year old, but his thumb was hanging on his hand and he could not use his strength. He did not know what the problem was before, but after reading my article, he realized that it was a floating thumb, and he wondered if a one-year-old baby could still have reconstructive surgery to save his five fingers. Floating thumb is a relatively rare hand deformity. The most obvious feature is the lack of metacarpal bone or only the remains of metacarpal bone, which causes the thumb to float like a small meatball hanging on the hand, and it can only swing with the swing of the hand. In the past, this condition could not be preserved, but had to be cut up and made into a thumb, which was very unfortunate. Nowadays, we save the five fingers with a hemi-metacarpal bone grafting technique, where the first metacarpal bone is reconstructed from a portion of the second metacarpal of the affected hand, and the chances of bone resorption and necrosis are greatly minimized. No other part of the child’s body is involved in the surgery, only the hand is operated, and the aftercare is not too troublesome. Semi-metacarpal bone graft reconstruction surgery is usually done when the child is around 6 months to 1 year old. It can help the child to establish thumb function as soon as possible, avoiding the habit of pinching objects with the middle and index fingers, and the child will not have the memory of the deformed features as well, which is better for the child’s physical and mental development. The surgery is divided into two phases, the first phase to move the bone, the second phase to establish the function, after the two phases of the surgery can be functional exercise, the appearance and function of the thumb will be improved very well.