Abstract: Fatigue failure caused by complicated stress in aeroengine firtree tenon-mortise is a common occurrence. The impacts on structure stress from the design parameters such as skew angle, wedged angle, and contact length, were studied by finite element analysis. This study provides a valuable reference for the design and optimization of firtree tenon-mortise. According to the geometrical characteristics of the four-teeth firtree tenon-mortise structure, some typical parameters are extracted, and a parametric modeling method of the firtree tenon-mortise structure is proposed. Taking into account the loaded modes and temperature effects on the tenon structure in practice, a thermo-structural coupling flow analysis of the firtree tenon-mortise structure is established by using the three-dimensional contact analysis. By changing the skew angle, wedged angle, and contact length, the stress distribution in the contact zone is calculated and the impact of each design parameter on structural stress is analyzed. The results show that increasing the skew angle leads to the higher local stress concentration in the mortise and the stress difference between the two sides of the tenon. An increased wedge angle results in the increase of stress load on the tenon-mortise, while the increaseed contact length will lead to the decreased contact stress. During the design process in aeroengine firtree tenon-mortise, it is recommended to keep the skew angle should below 20°, maintain a wedged angle between 18° to 20°, and adjust the contact length in an appropriate way.