The magnetorheological processing was investigated to improve the machining precision of large aperture optical elements. The principle of magnetorheological processing and the mathematical model of removal function were introduced. On the basis of the characteristics of the magneticrheological processing, the whole processing flow of optical elements was established and the technological factors of element process were given. Then, the software for extracting laser spots was developed, the technological software was also proposed based on the orbit segment divided speed mode and functions of modules in the technological software were analyzed. Finally, an element with a length of 800 mm and a width of 400 mm was machined experimentally. The results in low, middle and high frequencies by a test equipment show that the PV value of reflective wavefront in low frequency is 34 nm, the PSD1(power spectrum density)value is 1.7 nm, and the roughness Rq value is 0.27 nm, respectively. These experimental results verify that it is feasible to machine the high precise large aperture optical elements by magnetorheological processing. Moreover, this paper expounds the advantages of magnetorheological processing in high power laser component applications.