Rotational inertia measuring device

The invention discloses a rotational inertia measuring device comprising two oppositely-arranged bases and a spacer block used for connecting the bottoms of the bases and protruding toward one end. The bottoms of both the bases extend to the outer side to form base platforms, foot-pad screws penetrate the spacer block and one ends, away from the spacer block, of the base platforms, each foot-pad screw pads a foot pad, a gasket is arranged under each foot pad, the upper surfaces of the two bases are rails, a brake protrusion is arranged at one end of each rail, a graduated scale is arranged on the side face of each rail, a photoelectric door is mounted at the position of a zero mark of each graduated scale, and a rolling disc is arranged on the rails. A tested cylinder or tested ring can be mounted on the rolling disc, the inclination angle of the bases is adjusted through the gaskets, the distance from no movement to rolling of the rolling disc is determined through the bevel scales, movement time of the rolling disc is measured with a second chronograph, the photoelectric doors control timing to stop, the whole process is simple and easy to operate, and the rotational inertia can be measured accurately.