The invention discloses a device for testing tension of a test piece, and relates to a device used for the tension of the test piece. In order to solve the problems that the existing tension testing machine is complicated in structure, large in occupied area, high in cost, inconvenient to used in a manner of being matched with an optical measurement system, and poor in adaptability. The device for testing the tension of the test piece comprises a base, two sets of chuck components, two pretensioners and two top plates, wherein each set of chuck component comprises a chuck seat, a cover plate and a plurality of cushion plates; a groove is formed in the chuck seat; a threaded hole communicated with the groove is formed in the side wall of the chuck seat; the axial direction of the threaded hole is identical to the length direction of a test piece to be tensioned; the cover plate covers the upper surfaces of the cushion plates and is detachably connected with the chuck seat; the two top plates are arranged on the base in a face-to-face manner; the two sets of chuck seats are arranged on the base between the two top plates; the opening ends of the grooves in the side walls of the two sets of chuck seats are arranged in the face-to-face manner; and one end of each pretensioner is in threaded connection with the corresponding threaded hole. The device for testing the tension of the test piece is used in the fields of materials science, mechanics or optics.