Abstract: In order to promote the development of high efficiency and high reliability welding technology of large thick titanium alloy plate, the narrow gap laser-MIG composite welding technology of 60 mm thick TC4ELI titanium alloy plate was studied, and the narrow gap TC4ELI plate welded joint was obtained. The microstructure and mechanical properties of the welded joint were studied. The results show that the weld and HAZ structure of TC4ELI titanium alloy narrow gap laser-MIG composite welded joint are mainly composed of acicular martensitic α' phase, acicular α phase and a small amount of intergranular β phase. Under the influence of multi-pass welding heat, there are also lamellar or massive α phases in the middle weld and HAZ. The base material of the joint is α+β phase bistate equiaxial structure, and the structure distribution is uniform. The average tensile strength of different layer of the joint and the tensile strength of the metal deposited in the weld center are higher than that of the base metal. The microhardness and impact absorption energy of the welded joint from the weld center to the base metal tend to decrease. The bending performance of the joint is qualified. The narrow gap laser-MIG laser welding technology of large thick titanium alloy plate has a good application prospect.