Abstract: Elaborated here in the article are the mai n aspects of the NS3105 alloy U-shaped nuclear power- purposed tube, including the technical requirements, factors responsible for the wall thickness tolerance and relevant control actions. The key elements which need to be taken into consideration when conducting the process design for dimension tolerance of the straight blank tube before bending the NS3105 alloy U-shaped tube are presented, including the wall thickness inhomogeneity level of the straight blank tube, control of the wall thickness- reduction of the tube's arch section during bending process, after-bending polish-compensation, and the correcting effect on wall thickness inhomogeneity of the blank tube by the forming equipment and the operational tools.