Magnetorheological Finishing(MRF) is an advanced optical manufacturing technology, It is a kind of deterministic process. It conquers the defections such as low-efficiency and low-grade surface quality of the traditional method. Deduced from the hydrodynamic lubrication theory of the Bingham plastic flow, the material removal model of MRF is established. The reliability of the model is verified by the experiment. finally, we get the mean Preston coefficient by the theoretical curve and the actual measured curves, the value will be applied to optical components of the computer-controlled MRF operation. Through the magnetorheological finishing experiments , the results that compared with the experimental results in good agreement prove that our proposed model is reasonable.