Solid oxide fuel cell (SOFC) due to its high energy conversion rate and low noise can replace diesel energy as the submarine power. The interface thermal stress has an important effect on the stabilization and endurance of SOFC. The thermomechanical model of SOFC, which takes the interfacial layer into account, is developed to analyze the interfacial thermal stresses between electrodes and electrolyte in this paper. Based on the formation mechanism and composition distribution of the interfacial layer and the stress analysis of the half-cell system, the material property of the interfacial layer is determined and the interfacial thermal stress is expressed accurately. The finite element model of SOFC is employed to investigate the interfacial thermal stress, and the simulated result agrees well with the theoretical result. The modified expressions of interfacial thermal stresses for numerical result are given to analyze the difference between theoretical and simulated results at the free edge of SOFC. The anode-electrolyte interface needs to be concerned because its thermal stress level is higher and more likely to fail and partially delaminate compared with that of cathode-electrolyte interface. In addition, the optimization scheme with respect to the interfacial layer thickness is obtained and the interfacial thermal stress decreases with the increase of the interfacial layer thickness. The research provides guidance for determining and minimizing the interfacial thermal stresses of SOFC.