Abstract: To address the instability of riveting quality of TC4/TA2 dissimilar-thickness small V-shaped structural components for helicopters, the effects of welding process parameters on the formation and mechanical properties of spot welding joints were investigated based on the resistance welding method. A thermo-electro-mechanical coupled simulation model was established using ABAQUS software to simulate the formation process of TC4/TA2 titanium alloy resistance spot welding joints. The results show that the nugget of the TC4/TA2 spot welding joint gradually grows with the increase of welding time and shifts toward the TA2 side. The relative error between the experimental and simulated results is within 10%. Under the optimal welding process parameters, the tensile shear load of the joint reaches 6.73 kN, and the nugget diameter is 4.43 mm. The penetration rates on the TC4 and TA2 sides are 61.5% and 72.8%, respectively, and the surface indentation rate on the TC4 side is 13.0%. All parameters meet the requirements of aviation standards, and there are no defects such as spatters or cracks. The microstructure of the heat-affected zone on the TC4 side is composed of acicular α′ phase, primary α phase, and primary β phase, with the highest hardness (approximately 320 HV). The microstructure of the nugget zone is mainly coarse lamellar martensite α′ phase, with intermediate hardness (approximately 235 HV). The microstructure of the heat-affected zone on the TA2 side is mainly composed of massive α phase and a small amount of acicular α′ phase, with the lowest hardness (approximately 155 HV).