The invention belongs to the technical field of metallurgy and particularly relates to a method for preparing a motor shaft for nuclear power. According to the method for preparing the motor shaft for nuclear power, a raw material steel ingot is prepared through the electroslag remelting technology. The whole process includes the steps of material component optimization, motor production, electroslag remelting, forging and forming, treatment after forging, performance treatment and product machining. The problem that in the prior art, a motor shaft for a nuclear main pump shielding motor in the CAP1400 project cannot be produced is solved, and the method can be used on the nuclear main pump shielding motor and can be popularized in other nuclear power projects.