The invention discloses a tensioning type clamp for processing a piston. The tensioning type clamp comprises a pull rod, a spring, a clamp head and a clamp body, wherein the clamp body is connected with a main shaft of a machine tool, one side of the pull rod is glidingly connected with a groove, one end of the spring is connected with the bottom of the groove, the other end of the groove is connected with the end part of the pull rod, the outer part of one side of the pull rod is provided with a shaft sleeve in a sleeving way, a slide sleeve glidingly connected with the pull rod sleeves the outside of the other side of the pull rod, a step sleeve sleeves outside the shaft sleeve, the outer wall of the shaft sleeve is connected with the inner wall of one side of the step sleeve through screw threads, the inner wall of the shaft sleeve is connected with the pull rod through internal screw threads, the inner wall of the other side of the step sleeve is connected with one end, provided with external screw threads, of the clamp body through screw threads, the clamp head comprises a T-shaped movable block capable of entering a strip-shaped hole formed in the end part of the piston, and the end part of the long edge of the T-shaped movable block is connected with the end part of the other end of the pull rod. The tensioning type clamp overcomes the defects of poor fixation effect and low workpiece blank utilization rate during the clamping of the existing clamp. The invention provides the tensioning type clamp for processing the piston with the advantages that the fixation effect is good, and the blank cutting utilization rate is high.