<p>High temperatures can alter the physical and mechanical properties of surrounding rocks near tunnels and tunnel lining. Herein, the damage characteristics of these structures in the Xiamen Xiang’an Subsea Tunnel under high-temperature combustion and explosion were analyzed in depth using a combination of theoretical analysis, laboratory experiments, and physical model test. Results showed that the high-temperature degradation effects on the lining, weathered rock, and undamaged surrounding rock were significant, and the degree of degradation was closely related to their mechanical properties. When the temperature exceeded a certain critical threshold, the plastic deformation of the lining structure and weathered trough increased considerably. This critical threshold was closely related to the strength characteristics and deformation properties of the material at ambient temperature. Compared with those during explosions at ambient temperature, the strain values of the surrounding rock were larger under high-temperature combustion and explosion, whereas the peak acceleration was smaller.</p>