Floating thumb is a type IV thumb dysplasia, the most obvious feature of which is that only remnants of the metacarpal bones are present or completely missing, so the thumb hangs in the hand in a floating thumb state, unable to exert strength or hold things, and can only be corrected surgically. The floating thumb can be preserved, and the main surgical option we use is the hemi-metacarpal bone graft reconstruction technique. The surgery is divided into two stages, the first stage is to take part of the bone from the second metacarpal of the affected hand to reconstruct the first metacarpal, so that the thumb can have bone support and improve the shape of the thumb. After the bone is removed, the metacarpal bone in both the recipient and donor areas will regrow. After the first stage surgery, the bone needs to be fixed for a period of time and the second stage surgery can be performed only after the bone has healed. The second stage of surgery is to establish function and allow the thumb to move. After the two-stage surgery, the child will have to start functional exercises. Since children who have hemimelia reconstruction are usually quite young, parents need to play a guiding role when doing functional exercises by giving the child some toys that interest him so that he will realize that the thumb can move and he will be more and more willing to move.