The invention discloses an online automatic balance executing device for a high-speed electro-spindle rotor, which comprises a fixed disc, a moving disc and a moving disc support disc, wherein the fixed disc is mounted on a rotor end cover, the moving disc support disc is mounted on the high-speed electro-spindle rotor, the moving disc is mounted on the moving disc support disc, two induction transformers are arranged on the fixed disc and the moving disc support disc, the moving disc is internally equipped with a rotatable adjusting mechanism consisting of two groups of fixed rings and rotating rings, energy is sent by the primary induction transformer and received by the secondary induction transformer in an induction manner, piezoelectric ceramic sheets output by a driving circuit board to the fixed rings vibrate the fixed rings to realize in-plane standing wave vibration on the fixed rings, tooth-shaped protrusions on the fixed rings can poke the rotating rings periodically to drive the rotating rings to rotate, thus the relative position of two balancing weights is adjusted, the gravity center of the electro-spindle rotor is changed, and the purpose of online automatic balance for the high-speed electro-spindle rotor is reached; the device of the invention has the advantages of high precision, high safety, low pollution and adjustable balance weight capability.