Disclosed is a new spherical powder and a preparation method therefor. The method involves the steps of: placing an electrode and a workpiece at two electrodes of a power supply, regulating a discharging gap between the electrode and the workpiece by means of a motion control system to generate arc plasma, wherein the arc plasma acts on a surface of the electrode and the workpiece to melt the surface of the electrode and the workpiece, so as to form a melting region, and at the same time, introducing a fluid medium into the discharging gap, with the flow rate of the fluid medium being controlled and the relative rotation speed of the electrode or the workpiece being controlled, so as to cause the working morphology of the arc plasma to change, such that a tiny explosion is generated in the melting region to throw away and crush a material located in the melting region; and condensing the crushed material in the fluid medium, and collecting a condensed fine spherical powder. A hollow cavity is provided in the electrode or in the workpiece. The spherical powder prepared by the above-mentioned method has a small particle size, a regular particle shape, a good degree of sphericity, and a low content of a hollow powder and a satellite powder.