Abstract: Nuclear grade stainless steel welding joints were prepared by laser beam welding (LBW) at different welding speeds. Optical microscopy and scanning electron microscopy were subsequently used to study the weld penetration ratio, δ/γ ratio, micro structure, and phase composition. The hardness distribution was examined with a micro-Vickers hardness tester. When this welding speeds up, the weld penetration ratio and δ-ferrite content within the welding seam increase, the island and lath-shaped microstructures enlarge at the cost of the worm-like one, and the average hardness value in the weld area becomes greater.