Aiming at the influence of the thermoelectric leg size on the overall thermal stress field of the module in thermoelectric refrigeration modules， this paper takes the C-31106 thermoelectric refrigeration module as the research object and establishes a thermoelectric-mechanical coupled multiphysics field model composed of 31 pairs of thermocouples. Using the finite element simulation method， considering the existence of brazing layers and introducing the Anand modified constitutive equation characterizing the viscoplastic material， the thermoelectric model under three mounting conditions is established， and the influence laws of the height and the cross-section side length of thermoelectric legs on the temperature field and mechanical properties of the thermoelectric module under different currents are analyzed. The results show that when the thermoelectric leg is at the optimal height， the larger the cross-section side length of the thermoelectric leg is （within a given range）， the more favorable it is to improve the mechanical reliability of the thermoelectric module. When the operating current is 2.6 A and the cross-section side length is increased from 0.99 mm to 1.09 mm， the maximum von Mises stresses at the hot and cold sides are reduced by 74.67% and 22.60%， respectively. The mechanical reliability of the thermoelectric module can be improved by using fixed constraints and mechanical press-fit mounting for the cold and hot sides of the module， respectively. The maximum von Mises stresses on the hot and cold sides of the module are reduced by 48.76% and 74.02%， respectively， compared with the fixed restraints on both sides.