The characterization of the deterministic material removal plays an important role in the ion-beam figuring (IBF) polishing process, which is used to predict the material removal and help to determine the dwell time needed at different positions of the workpiece. The ion beam etching characteristics of fused quartz optical components were studied by radio frequency(RF) ion source, the precise removal function was calculated and obtained by using ZYGO interferometer, and the influences of the plasma source operational parameters such as work gas mass flow rate, screen voltage, incidence angle of ion beam and work distance on the material removal function of fused quarts were investigated. Furthermore, the relative change rates of the material peak removal rate, the full-width-at-half-maximum (FWHM) of peak and the material volume removal rate were measured and calculated when individual work parameter was perturbed. The experiment results show that the variation of removal functions varies slightly with the gas mass flow rate under the same work vacuum pressure. It is found that the relative errors of the removal function′s peak removal efficiency, the FWHM and the volume removal efficiency can all controlled in 5% when the screen voltage fluctuation is ±5 V, the incidence angle deviation of ion beam is ±1° and the work distance deviation is ±0.5 mm, respectively. Hence the removal function of IBF for fused quartz by using RF focusing ion source has better certainty and stability.