The invention provides a thermal fatigue experimental device which comprises a working frame, a laser heating system, a sample placing seat, a temperature measuring device, a crack observing device, a cooling device and a control unit, wherein the working frame comprises a laser fixing frame; the laser heating system is mounted on the laser fixing frame and is used for heating a sample; the sample placing seat comprises a clamping device for fixing the sample and is positioned under a laser generator, and the clamping device comprises two oppositely-arranged clamping blocks and a power device for driving the two clamping blocks to relatively move; the temperature measuring device is used for monitoring the temperature change of the sample in the experimental process in real time; the crack observing device is used for monitoring the state change of the surface of the sample in the experimental process through image equipment; the cooling device is used for reducing the temperature of the sample; the control unit is used for controlling experimental parameters of each part. The thermal fatigue experimental device provided by the invention has the benefits that the sample is subjected to constant mechanical stress loading while undergoing thermal cycling temperature fluctuation, a directional expansion crack can be generated in the direction parallel to comprehensive load, and the thermal fatigue property test on a material sample and a structural part can be met, so that the scientific significance and engineering value are important.