The utility model discloses a nuclear-grade ejector which comprises a working fluid inlet pipe, a driving fluid inlet pipe, a receiving pipe and a straight pipe segment, wherein the working fluid inlet pipe comprises an inlet shrinking pipe which is designed to be of a conical structure, and the necking size of the inlet shrinking pipe is phi 16.5mm. Compared with the prior art, the nuclear-grade ejector is enabled to conduct reasonable design on the size of each element, can ensure that a containment spray system is safely put into operation when an LOCA accident occurs in an reactor or a main steam pipeline is ruptured, and has the advantage of being stable and reliable in performance, and therefore effectively ensuring safe operation of a nuclear power plant.