This article expound 150 mm bearing plate welding process of the sea-river-through direct ship channel cable steel tower of Hong Kong-Zhuhai-Macao bridge assembly and welding technology without temporary piece clamp plate from design of beveled edges,selection of welding material,welding procedure qualification and welding process control. The feasibility and rationality of welding technology are verified by welding process evaluation test. Through welding deformation monitoring,overturning welding and nondestructive testing,the welding deformation of super thick plate is effectively controlled and the quality of welding seam is guaranteed.