Abstract: An adaptive control algorithm is proposed in centreless pass-grinding system, in order to change the centreless pass-grinding situation of manual detection and adjustment, stabilize and improve work-piece's machining quality and accuracy.It constructs the mathematics' model of difference equation including nonstationary interference according to the features of centreless pass-grinding system and work-piece-error sequences.The self-tuning controller of pole-placement is designed used for machining accuracy in the centreless pass-grinding system, which is combined the estimating parameters algorithm with the pole-placement algorithm.The pricinple of pole-placement is to ensure the system's stability.The experiment and simulation results show that the pole-placement algorithm has advantages of improving the system's performance of machining accuracy and stability compared with Fuzzy-PID algorithm.