The invention relates to a floating type centering device for a connecting arm. A first base on a base plate is provided with a connecting arm positioning shaft; a horizontal guide rod is movably arranged in a second base on the base plate; the V-shaped positioning block is positioned between the first base and the second base; the side, close to the second base, of the V-shaped positioning block is connected with the horizontal guide rod, and the side, away from the second base, of the V-shaped positioning block is provided with a V-shaped positioning groove. The central axis of the V-shaped positioning groove is collinear with the straight line; the elastic floating piece is installed on the second base and connected with the V-shaped positioning block. During centering, one end of the connecting arm is directly connected with the connecting arm positioning shaft, then the other end of the connecting arm is clamped with the V-shaped positioning groove, the center of the workpiece is aligned according to the V-shaped self-centering principle, and centering is completed. When the thickness of a workpiece blank fluctuates, the V-shaped positioning block moves in the limiting direction of the horizontal guide rod due to thickness fluctuation, the elastic floating piece is compressed, it is guaranteed that the V-shaped positioning block is attached to the workpiece all the time, the whole workpiece does not deviate or rotate, and the floating centering effect is achieved.