Abstract: To solve the problem that tool paths will bring iterative errors in the process of magnetorheological polishing, an adaptive polishing path method is proposed, in which the step size can be adjusted according to the optical surface gradient. Firstly, according to the distribution of the original surface errors, all the gradient values at each point can be obtained and will be classified based on the discrete gradient clustering. Then a tool path that both the row and column step size can be adjusted with respect to the surface errors is obtained. Experiments on the home-made magnetorheological finishing machine MRP-1200M successfully process a 50 mm diameter microcrystalline glass, from 65 nm(PV) and 12 nm(RMS) to 21 nm(PV) and 2.5 nm(RMS) without obvious peak error in the power spectral density curve after processing. Experimental results show that this adaptive tool path can effectively suppress the mid-spatial errors and the high-spatial errors.