Hong, Z. Diao, Q.S. Li, M. Lian, H. JACoW Publishing Geneva, Switzerland In this paper, a machining scheme of magnetically controlled small tool was proposed, which gets rid of the limitation of the power system and transmission system, and realized the free machining of channel-cut crystal with narrow space, a high quality channel-cut crystal with high wavefront maintenance and high transmission efficiency in a large size range was obtained. The results of offline characterization showed that: The roughness of inner surfaces reached 0.6nm RMS; Microstructure analysis show that the perfect lattice substrate was only covered 2.5nm thickness uniform SiO₂ layer, and there was no uneven bending of the oxide layer caused byμstress concentration. The results of online tests showed that: the Darwin widths of the channel-cut crystal processed by MC-CMP were consistent with the theoretical values, the two diffraction reflectivity rate of the crystal reached 85.1\%, very close to the theoretical limit of 88.3\%. The morphology of channel-cut crystal treated by MC-CMP technology was uniform, scratches and spot defects were eliminated completely. The wavefront equivalent crystal profile error of the two diffraction reached 130nrad RMS with 5 mm dimension.