Aiming at the mismatched disturbance problem caused by the jet reaction force at the end of the rust removal sandblasting parallel mechanism, a nonlinear Active disturbance rejection control method of the rust removal sandblasting parallel mechanism was proposed. Firstly, the kinematics of the parallel mechanism was analyzed by the analytical method, and the dynamic model of the parallel mechanism considering the mismatched disturbance was established by the Lagrange method. By applying equivalent input disturbance technique, the mismatched disturbance of the system was converted to the matched disturbance located in the control input channel, and the total disturbances of the system was aggregated with modeling error, joint friction force and external disturbance. The nonlinear extended state observer was designed to estimate and compensate the lumped disturbance accurately in real time. The active disturbance rejection control based on the extended state observer was further designed to enhance the robustness of the system to lumped disturbance and improve its trajectory tracking control performance. Finally, the stability of the closed-loop system was proved, and based on MATLAB software and the prototype of the parallel mechanism with jet reaction force for rust removal sandblasting, the proposed control method was simulated and tested. The experimental results verify the effectiveness of the proposed method.