Abstract: Crack is the main defect of dissimilar metals circumferential weld in nuclear industry. The crack of dissimilar metals circumferential weld had been analyzed and controlled from chemical composition, backing welding technology, welding heat input and constrained state. Weld performances were valuated by X-ray examination, metallographic examination, and residual stress analysis. The circumferential weld crack had been eliminated and the residual stress had been decreased. The results has good reference for the control of dissimilar metals circumferential weld crack.