Abstract: In order to analyze the influence of the friction torque change on the measurement of rigid body inertia, the falling body method is used in the experimental analysis. It is indicated that the friction torque increases significantly with the increase of the system rotation speed, if the average rotation speed of the system in the deceleration process is much higher than that in the acceleration process, and if no correction is made, the calculation results are usually relatively small. At the same time, it is pointed out that the average rotation speed in the acceleration process and the deceleration process are relatively close to each other, the measuring value is mainly affected by the random error. The above results are helpful to further study the friction torque variations against the rotational speed.