Abstract: Underground coal gasification （UCG） is a critical pathway for the green and efficient development of residual coal resources in closed mines. During the gasification of residual coal, the movement and failure of the overburden structure are subjected to the coupled disturbances of lateral legacy goafs and high-temperature thermal damage fields, posing significant challenges to surrounding rock stability control and disaster prevention. To address this issue, based on a systematic analysis of the evolution of thermo-mechanical parameters of coal and rock at elevated temperatures, a thermo-mechanical coupled numerical simulation method for gasification mining is developed, considering the coupled variations of high-temperature thermodynamic parameters. Numerical simulations are conducted to investigate the response characteristics of surrounding rock movement and failure under lateral goaf disturbances during underground gasification of residual coal. The results indicate that the expansion of the temperature field during gasification drives the synchronous development of the surrounding rock’s thermal damage field, thereby causing simultaneous variations in the thermo-mechanical parameters of the surrounding rock. Owing to parameter degradation, the boundary of the thermal damage field lags slightly behind the temperature front. Influenced by the lateral goaf disturbance, the vertical stress on the coal pillar flanking the goaf undergoes a significant leap, inducing a drastic expansion of the failure zones in both the roof and the pillar. Specifically, the roof failure height increases by 260%, and the pillar damage width increases by 40%, with the plastic failure zone exhibiting a distinct asymmetrical development biased toward the goaf side. Furthermore, the lateral disturbance triggers the reactivation of the legacy goaf, significantly exacerbating surface subsidence and roof movement. Under single-side goaf influence, the peak vertical displacements of the surface and roof increase by 66% and 67%, respectively; under double-side goaf influence, the maximum increments reach as high as 134% and 93%, respectively. These findings reveal the response mechanisms of surrounding rock under thermo-mechanical coupling during residual coal gasification and provide a theoretical basis and technical support for design optimization, surrounding rock stability control, and disaster prevention in gasification mining.