A device for bone fixation, comprising: an expansion part having an end being a fixing end and another end being a top end, and having an expansible structure which is adjustable between a state of expansion and a state of contraction; a covering part having an end being a front end and another end being a joining end, wherein said front end is joined to said top end, said joining end is secured to said fixing end, and said covering part covers said expansion part; said expansion part and said covering part being adapted to be placed in a bone, said covering part being adapted to be propped up by said expansible structure when said expansible structure is expanded into the state of expansion; a hollow joining tube having a front end and a rear end, wherein the front end of the hollow joining tube is detachably joinable to the fixing end of said expansion part; an auxiliary expansion part having an end being a coupling end and another end being an operating end, wherein said coupling end is detachably joinable to the rear end of said hollow joining tube; an operating shaft having an end being a front end, and another end being a rear end, wherein the front end of said operating shaft is detachably joinable to said expansion part, the rear end of said operating shaft is joinable to the operating end of said auxiliary expansion part, and said operating shaft is operable to adjust the expansion part between the state of expansion and the state of contraction; an injection tool being joinable to the rear end of said hollow joining tube or the rear end of said operating shaft, the injection tool being adapted for injecting or pushing a medical filler into said covering part via said hollow joining tube or said operating shaft. an expansion part having an end being a fixing end and another end being a top end, and having an expansible structure which is adjustable between a state of expansion and a state of contraction; a covering part having an end being a front end and another end being a joining end, wherein said front end is joined to said top end, said joining end is secured to said fixing end, and said covering part covers said expansion part; said expansion part and said covering part being adapted to be placed in a bone, said covering part being adapted to be propped up by said expansible structure when said expansible structure is expanded into the state of expansion; a hollow joining tube having a front end and a rear end, wherein the front end of the hollow joining tube is detachably joinable to the fixing end of said expansion part; an auxiliary expansion part having an end being a coupling end and another end being an operating end, wherein said coupling end is detachably joinable to the rear end of said hollow joining tube; an operating shaft having an end being a front end, and another end being a rear end, wherein the front end of said operating shaft is detachably joinable to said expansion part, the rear end of said operating shaft is joinable to the operating end of said auxiliary expansion part, and said operating shaft is operable to adjust the expansion part between the state of expansion and the state of contraction; an injection tool being joinable to the rear end of said hollow joining tube or the rear end of said operating shaft, the injection tool being adapted for injecting or pushing a medical filler into said covering part via said hollow joining tube or said operating shaft.