The invention relates to an apparatus for testing thermal fatigue of cylinder covers. The apparatus comprises a basic testing platform and a data acquisition and control system. The basic testing platform comprises a false cylinder 1-3, a cylinder cover 1-4, exhaust guide tubes 1-5 and an exhaust collector 1-6, and further comprises a high-low temperature binary constant temperature cooling system 1-2 and a diesel supply and flame heating system. A cylinder gasket is arranged between the false cylinder 1-3 and the cylinder cover 1-4, and the false cylinder 1-3 and the cylinder cover 1-4 are fixedly connected through cylinder cover bolts. The apparatus for testing the thermal fatigue of the cylinder covers can be used for simulating the cylinder covers under the actual state of bearing situation, time for testing can be shortened fast, and security degrees during testing are high. The invention further discloses a method for testing fatigue of the cylinder covers corresponding to the apparatus for testing the thermal fatigue of the cylinder covers.