High-temperature-resistant enamel coatings have been reported to be applied in non-critical hot end components of aero-engine and gas turbine recently. Although the enamel with a series of excellent properties can be as high-temperature-resistant coating material under appropriate condition, its lower soft point and inherent brittleness limit their use in broader application under severe service condition. Enamel-based composite coatings (an enamel matrix with the addition of ceramic particles and/or metal platelets) can remarkably increase the properties of the enamel coating and their protection mechanism under dynamic thermal shock needs further investigation. In this work, two kinds of enamel-based composite coatings, 70%enamel+25%Al₂O₃ and 70%enamel+20%Al₂O₃+10%NiCrAlY (mass fraction, %) abbreviated to E25A and E20A10M respectively, were designed and fired on K38G superalloy substrate, and their protection mechanism was comparatively studied at 900 ℃ under the simulated combusting gas shock. The thermal shock fire was produced by the mixture gas of C₃H₈+O₂ and its ejecting pressure on the coating surface was 0.4 MPa. After the temperature has been stable at 900 ℃, samples were hold for 15 s and then cooling down in air for 120 s, constituting a thermal shock cycle. Results indicated that, after 150 cyc of thermal shock, both the coatings bond well with the alloy substrate, thus shows high resistance to spallation along interface. For the E25A coating, its microstructure had no obvious change after thermal shock and the surface is still intact. The addition of secondary phase Al₂O₃ increases the stability of enamel at high temperature. With regard to the E20A10M coating, holes and cracks form consecutively, and peeling off occurs at surface after thermal shock. Interfacial reaction between the NiCrAlY particles and enamel following Cr_(NiCrAlY)+ZnO_(enamel)→CrO_(interface)+Zn↑ results in the formation of enamel swelling, which then, under the synergistic effect of combusting gas shear stress and interface thermal stress, leads to the peeling off of enamel and metal inclusions at surface.