Holistic forming high-performance and high-quality shielding sleeve is a major issue to be resolved urgently in independent manufacturing of China's nuclear power equipment. The mechanism of flaring for spinning thin-walled tube was analyzed by finite element simulation, and the influences of the wall thickness and start-spinning position on flaring height were researched. The analysis result shows that when the wall thickness increases and the start-spinning position is far away from the end, the flaring height decreases. Furthermore, the craft port structure to restrain the ends expanding is proposed and verified by spinning experiment. The results show that the suitable craft port structure can effectively restrain the flaring height of the end portion and can improve the overall stiffness of the spinning component.