The invention discloses a centrifugal machine test-piece horizontal reversing locking device. The centrifugal machine test-piece horizontal reversing locking device comprises a rotary test platform used for installing a test piece. An installment hole is formed in a rotary arm of a centrifugal machine; the rotary test platform is installed in the installment hole through a fixing device; the fixing device comprises a reversing pin and a locking module; a pin groove is formed in the position, close to the edge of the rotary test platform and the center of the rotary arm, on the rotary arm; the reversing pin is arranged in the pin groove and can move; a handle extending out of the rotary arm is arranged on the reversing pin; a pin hole matched with the reversing pin is formed in the edge of the rotary test platform; the rotary test platform and the rotary arm are locked and fixed through the locking module. The horizontal angle of the rotary test platform is fast positioned through the reversing pin, the reversing pin will stay in the pin hole all the time under the action of centrifugal force, and will not move, the rotary test platform and the rotary arm are fast locked and loosened through the locking module, and accordingly reversing and locking operation can be fast and conveniently conducted on the rotary test platform and a test piece.