The invention relates to the field of power machines, in particular to a rotational inertia impeller, and aims to solve the problem that several power devices cannot effectively use inertia. The rotational inertia impeller comprises a shaft 1 and blades. The inner ends of the blades are connected with the shaft 1. The blades are common blades or inertia blades 7. The turning radius R0 of each inertia blade 7 is 0.72 times larger than or equal to the length R1 of the inertia blade. The rotational inertia impeller further comprises a first inertia heavy cycle 8, which is fixedly connected or hinged to the outer ends of the inertia blades 7. The weight of the first inertia heavy circle is 0.38 times larger than the total weight of the inertia blades 7, or/and the rotational inertia impeller further comprises a second inertia heavy circle 9, which is fixedly connected with the shaft 1 through a bracket 2. The rotational inertia of the second inertia heavy circle 9 is a times of the total rotational inertia of the blades, wherein a ranges from 1 to 8. The rotational inertia impeller can be widely applied in fields, such as a water turbine, a wind turbine, a steam turbine, an electric motor, an airplane and a vessel, and a power device is enabled to use the inertia of the blades and the inertia heavy circles to the greatest degree, so that the purposes of saving energy and improving efficiency are achieved.