Abstract: T-nozzle is the inlet of the mixture gas of hydrogen and steam in a hydrogenated reactor.Many cracks have been generated in T-nozzle,which are caused mainly by the welding residual stresses.Finite element method is used to study the welding residual stress in T-nozzle of hydrogenated reactor.Based on considerations of residual stress,the welding structure of T-nozzle is optimized.The axial of T-nozzle is welded in the direction of head radius,through which the stress concentration is decreased.Large residual stresses are generated in the internal surface of nozzle and head,which have great effect on stress corrosion cracking.A flanging is inserted into the nozzle to isolate the residual stress from the mediums,which can prevent the stress corrosion cracking.It can be a reference for crack treatment and structure optimization of T-nozzle for hydrogenated reactor.