A large-diameter thin-walled high temperature alloy tube with serrated groove is produced by inner spinning whose blank is welded up, and the micro-hardness and microstructure characteristics of the serrated groove in the tube are investigated. The welding results in coarse and uneven dendrites in the as-welded joint, which leads to larger the micro-hardness difference between the as-welded joint and the out of -welded joint zone. Both the original grains from the outer of the welded joint zone and the dendrites of the as-welded joint are refined by the inner spinning on the serrated groove. The micro-mechanical property unevenness of the serrated groove is significantly improved by severe plastic deformation.