Abstract: The argon arc welding process of TC4 /TA18 dissimilar titanium alloys for UAV titanium alloy truss structures was systematically studied. By optimizing process parameters such as welding current and shielding gas flow, weld joints with good formation and no defects were obtained. The microstructure evolution, element distribution, phase composition and mechanical properties of the weld joints were analysed using OM, SEM, XRD and other testing techniques, illustrating the correlation between the microstructure and mechanical properties in different regions of the weld joints. Targeting the welding characteristics of truss structures, specialised welding and heat treatment fixtures were designed to effectively control welding deformation of truss structures. The results show that under the parameters of welding current of 30 A and shielding gas flow of 10 L/min, the microhardness distribution of the joint is uniformly distributed, and the mechanical properties at room and high temperatures meet the service requirements. The joint strength of the welded joint is higher than 80% of the TA18 base material. The fixtures can effectively controll the welding deformation. The welding process possesses good prospects for engineering applications