The invention discloses a narrow clearance TIC automatic welding technique for a thick plate of titanium alloy. The welding technique comprises six items of a welding torch form, a welding line spreading form, a bevel for welding form, selecting the parameters of the welding process, selecting the protection atmosphere of the welding process and eliminating a welding stress adopted by welding process. The welding technique of the invention realizes the narrow clearance welding for the large thick plate of the titanium alloy, has stable welding process, can obtain the welding lines which have no defects, qualified properties and 10mm to 16mm of widths of the welding lines on a cover surface layer, thus solving the key technical problems of the narrow clearance TIC automatic welding for the large thick plate of the titanium alloy, realizing the narrow clearance TIC automatic welding for the thick plate of the titanium alloy and having the advantages of high manufacture efficiency, low manufacture cost, small residual stress and residual deformation of joints, relatively thin and small welding line tissues and good mechanical property of the joints.