Abstract: Liquid hydrogen, with its high energy density, clean and pollution-free properties, has become a key focus in the unmanned aerial vehicle （UAV） industry. As a core component of liquid hydrogen UAVs, the thermal insulation performance and weight of liquid hydrogen tanks significantly impact the UAV's endurance and maneuverability. Finite element methods were employed in this study to conduct a thermal-mechanical coupling analysis of a UAV liquid hydrogen tank and proposes lightweight modifications for the tank. The LBL model was used to calculate the apparent thermal conductivity of multi-layer insulation structure for the tank, which resulted in 0.46 W/（m·K）. Theoretical calculations and simulation results yielded heat leakage values of 1.13 W and 1.26 W, respectively. When filled with liquid nitrogen, the simulated heat leakage was 1.03 W, deviating by 5.10% from the experimental result of 0.98 W, thereby validating the reliability of the simulation prediction method. Stress analysis conducted under full-load conditions revealed maximum stresses and deformations of 66.94 MPa and 0.27 mm, respectively. An analysis of four hazardous operating conditions was conducted. Based on the combined stress and deformation results, the emergency braking condition was identified as hazardous. Stress verification was performed at the structural discontinuity locations. The verification results indicate that the maximum stresses in the storage tank during this condition remain below the allowable values. Using the response surface method, an equation was developed to relate tank stress to the wall thicknesses of the inner and outer vessels. Within a specified range of wall thickness, the minimum values that did not exceed the allowable stress limit were identified. The optimized inner and outer container wall thicknesses were determined to be 0.80 mm and 1.20 mm, respectively, meeting the strength requirements. The empty weight decreased from 11.31 kg to 9.77 kg, while the mass hydrogen storage ratio increased from 16.28% to 18.38%. This study provides a theoretical reference for the structural optimization and design of liquid hydrogen storage tanks for unmanned aerial vehicles.