Abstract: The application of fluid jet polishing (FJP) technology, who has unique advantage in machining ultra precision optical elements, is limited due to low removal efficiency.The effects of nozzle diameter and jet pressure on removal function, removal efficiency and deterministic modification are analyzed by experiments and simulations.It is experimentally ascertained that the removal efficiency increases with the increase of nozzle diameter in a certain size range, and that the removal efficiency increases slower when nozzle diameter increases beyond the range.The width change of the removal function is much larger than that of the nozzle diameter.The depth of the removal function increases exponentially with the increase of the jet pressure, and the profile of the removal function changes from W shape to double W shape.By establishing the rotation function to simulate the eccentric rotating jet method, it is proved that the removal function after deformation has good applicability in deterministic polishing process and the method can be directly applied to the deterministic polishing of the ultra precision surface using a vertical jet.