Magnetorheological Finishing (MRF) was an advanced optical machining method. The removal material was related with the dwell time when the work-piece was machined with MRF. On the base of analyzing the effect of machining parameter and the principle of surface control, the MRF dwell time algorithm based on matrix was presented according to Preston equation. The symmetry axis curve surface, such as aspheric surface, which was fit for optics general equation, was machined with MRF machine by using this interpolated algorithm. Simulation experiment results show that the spherical surface error can be constricted less than 20 nm by using the dwell time algorithm. The planar and spheric K9 optics glass was machined with MRF by using the dwell time algorithm, and the spherical surface, whose Ra is 0.636 nm and PV is 52.14 nm, is acquired.