Micro-milling is extremely paramount to fabricating micro-scaled components , requiring high quality and low setup cost. However, with the stiffness of low micro-milling systems, the uncontrolled surface and vulnerable wearing tools must be addressed to achieve ultra-precision processing for the thin-wall microstructure . This paper explored the mechanism of surface formation based on dual-direction vibration-assisted micro-milling , and verifies the effectiveness in back chipping, analyzing the impact on chips and tool life-lengthening effect. Initially, an active vibration-assisted signal was added to the feed direction, considering the impact on surface integrity and qualit y, a nd the integrity and quality of the machined surface model were examined. Furthermore, two groups of experiments assessing the micro-milling Co41Cr16Ni15 alloy were carried out , comparatively with conventional micro-milling, analyzing the effect of the vibration-assisted device on surface integrity and quality , and a deterministic vibration-assisted micro-milling system was established. Finally, the effects of vibration assistance on surface topography, chip topography and micro-milling tool runout were determined. As a result, vibration assistance improved the micro-step structure on both sides of the thin-wall microstructure surface caused by tool eccentricity, and changed the surface morphology of the groove bottom. The experiment results showed that the form deviation of the vibration-assisted micro-milling surface was less than 101 nm SPV and surface roughness was also below 25 nm RMS. Surface formation mechanism based on the vibration-assisted micro-milling system was explored to reveal that vibration assistance improves surface integrity and quality , and sharply reduces the tool’s runout rate.