To address the problem that the damage mechanism of the annular combustor of a certain type of aero-engine remains unclear, based on the finite element simulation calculation software Ansys Workbench, the numerical simulation research on the non-premixed combustion process of a certain type of annular combustor was carried out by adopting the fluid-solid-thermal coupling simulation method. The fuel combustion process occurring in the combustor was simulated, the temperature distribution of the flow field under typical working conditions was compared, and the plastic strain distribution of the flame tube during the operation of the engine was explored. By comparing the temperature field distribution of the combustor under the conditions of different grid numbers in the fluid domain and different chemical reaction mechanisms of alternative fuels, and comparing it with the results of the borescope inspection during the actual service process of the engine, the accuracy of the model was verified. The results show that during the process of analyzing the damage mechanism of the combustor, the surface temperature of the flame tube calculated based on the Z77 mechanism is closer to the actual damage distribution of the combustor. The low-temperature air flowing into the combustor through the primary combustion holes and mixing holes on the wall of the flame tube will cause a relatively high temperature gradient on the wall surface, resulting in uneven local thermal expansion of the flame tube and leading to a relatively high level of thermal stress. This further results in the concentration of high-intensity plastic strain below the mixing holes, which is the main cause of the initiation and development of cracks.