The invention discloses a center-aligning floating clamping fixture used in a machine tool for two ends of a steel pipe. The structure of the center-aligning floating clamping fixture comprises a fixture supporting frame, a driving mechanism, a transmission mechanism, a clamping mechanism and a floating aligning mechanism, wherein the transmission mechanism and the clamping mechanism are connected with each other, the clamping mechanism is provided with two chuck uprights which are parallel to each other in opposite directions, the uprights are provided with V-shaped jaws and connected with a bracket, a V-shaped clamp is provided with two pairs of floating clamping blocks, clamping surfaces of the clamping blocks are multidentate clamping surfaces, and the multidentate clamping surfaces are positioned on a same cylindrical surface. The center-aligning floating clamping fixture can be used for special machine tool equipment for machining the two ends of the steel pipe of a DT II type roller of a belt conveyor, and the geometric axis center of the steel pipe to be automatically aligned with the axis center of the machine tool so as to control radial deformation of the steel pipe.