This study investigates the cryogenic tensile properties and fracture behavior of fiction stir welded and post-weld heat-treated joints of 32Mn-7Cr-1Mo-0.3N steel.Cryogenic brittle fracture,which occurred in the as-welded joint,is related to the residual particles that contain tungsten in the joint band structure.Post-weld water toughening resulted in the cryogenic intergranular brittleness of the joint,which is related to the non-equilibrium segregation of solute atoms during the post-weld water toughening.Annealing at 550 ℃ for 30 min can effectively inhibit the cryogenic intergranular brittleness of the postweld water-toughened joint.The yield strength,ultimate tensile strength,and uniform elongation of the annealed joint are approximately 95%,87%,and 94% of the corresponding data of the base metal.