The invention discloses a pneumatic liquid type rotor online automatic balance executer, belonging to a novel structure in the field of liquid type balance. Balance liquid is injected into four liquid storage chambers at a time, pressure gas drives the balance liquid to move directionally between opposite liquid storage chambers, and the process of injecting liquid from outside of the existing liquid type balance executer is replaced. A rotary part is not provided with movable components such as an electromagnetic valve, a check valve and the like, and a bearing only realizes a function of connecting the movable and static parts and does not bear load. The gas pressure is transferred between the static and movable surfaces without contact, and a sealing material is not required. The liquid with proper density and stable performance can be selected as the balance liquid, and the consumption thereof is nearly zero. The pneumatic liquid type rotor online automatic balance executer disclosed by the invention can be designed into multiple structural styles according to the actual demands so as to adapt to different mounting ways and different balance requirements, and has advantages in the aspects of balance performance such as balance quality, balance speed and the like, balance ability, long-time stability and the like.