The invention discloses a torsion testing device of a fiber reinforced composite material. The device comprises a rack, a motor, a guide rail, a draw-off mechanism and a rotary clamp and a positioning clamp for clamping the fiber reinforced composite material, wherein the motor is arranged on the rack in a manner that a rotating shaft is horizontally placed, the rotary clamp is connected with the rotating shaft of the motor, the guide rail is arranged on the rack in front end of the rotating shaft of the motor, the positioning clamp is slidingly connected with the guide rail and capable of enabling the fiber reinforced composite material between the rotary clamp and the positioning clamp to place on an axle position of the rotating shaft of the motor; the draw-off mechanism is connected with the positioning clamp, and capable of drawing the positioning clamp to slide to a stretched straight direction of a test sample through self weight. The device is capable of accurately controlling the time of contra-turning angles and the time for finishing the angle contra-turning, high in automation degree, precise and reliable in test result and capable of avoiding accidental error in manual operation.