Ion Beam Figuring (IBF) technology was investigated for application to a high-precision optical aspheric. With the analysis of the IBF system, the motion model formulas of an ion source subsystem were presented for figuring aspheric optics and other optics by the IBF facility. The de-convolved process of the dwell time function was transferred to a linear matrix equation, which could be easily optimized to get the optimized dwell time solution. Using an analysis of the location errors, this paper proposes that the final figure errors caused by the location errors of the ion source five-axis motion subsystem could be attributed to a coefficient factor. The best way to avoid the location precision requirements is to take both the ion beam material removal function and the location errors into account in designing the five-axis system accurately. The simulation example proves that the dwell time function obtained from this model is effective in assuring the final optical element figure precision(0.038 1λ).The final optical element figure errors from the location errors of the ion source five-axis motion subsystem are bound by the range of maximum difference. So this model can be used for all kind of optics to determine the dwell time function and to design the location subsystem error precision, and also to assure that the IBF process is stable and feasible at the minimal cost.