Slender shaft is often adopted chuck-thimble type clamping method for processing. It is difficult to ensure the precision after processing due to the low stiffness and rigidity different at different locations. In order to solve problems of lower accuracy and improve the precision, a new process of three-dimensional (3D) moving cutting fluid servo mirror support is designed. The dimensional error mathematical model based on cutting fluid follower radial support elongate shaft machining process was established. Finally, the reliability of cutting fluid follower mirroring support process was verified by experiment. The results show this process can ensure higher precision than the machine process with rest support.