In order to further improve the dimensional accuracy of micromilled thin walls with high aspect ratios, the machining process should be actively controlled. An active cutting force measurement and cutting parameter compensation device is developed to realize the real-time measurement of radial cutting forces and compensation of radial cutting parameters in thin wall cutting process. Firstly, based on the cantilever beam deformation theory, a mathematical model is established to calculate the deformation and cutting force of thin walls. By measuring the cutting force, the thin wall deformation in the cutting process could be estimated. Then, the obtained incremental thin wall deformation is to be compared with the compensation threshold, which is set at 0.5 μm. If the value of the incremental deformation is less than 0.5 μm, compensation will not be processed. Otherwise, the incremental deformation is used as the compensation value for iterative compensation, until the incremental deformation of the thin wall is less than 0.5 μm. At last, a contrast experiment is carried out. The experimental results show that the introduced device and method are feasible. Machining quality of the thin wall has been obviously improved in dimension precision after the cutting parameter compensations.