The invention discloses a vacuum heat expansion forming process of a rotor shielding sleeve of a nuclear main pump, which is mainly used for shaping the rotor shielding sleeve of the nuclear main pump and belongs to the field of nuclear power. The rotor shielding sleeve is sleeved outside a die at normal temperature; the rotor shielding sleeve and the die are placed in a vacuum heat treatment furnace; and with the rise of the temperature, since a linear expansion coefficient of the die is larger than a linear expansion coefficient of the rotor shielding sleeve, the rotor shielding sleeve is subjected to heat expansion force action of the die to generate plastic deformation. In the heat-preservation stage, the stress of the rotor shielding sleeve is reduced and creep deformation occurs according to the stress relaxation principle. When the rotor shielding sleeve and the die are cooled to room temperature, the plastic deformation and the creep deformation of the rotor shielding sleeve can be retained, thereby achieving the shaping aim. On one hand, the invention can ensure the forming precision and the roundness of the rotor shielding sleeve and the forming quality of the rotor shielding sleeve is stable; and on the other hand, the invention simplifies the production process flow, reduces the production cost and saves the production cost.