In order to obtain the effect of ion source parameters on etching rate and surface roughness in the process of ion beam etching polishing.We used the microwave ion source as the etching ion source, took benzocyclobutene (BCB) as the object of study, and did the research of the effect of ion source parameters,including the energy and current density of ion beam, the quantity of oxygen and argon,on etching rate and surface roughness,and then obtained the relationship between the ion source parameters and the etching rate, roughness evolution.It turns out that in the process of ion beam energy increasing from 400eV to 800eV, the etching rate increases constantly, increasing from 3.2 nm/min to 16.6 nm/min; in the process of ion beam current density increasing from 15 mA to 35 mA, the etching rate increases constantly, increasing from 1.1 nm/min to 2.2 nm/min; in the process of quantity of oxygen increasing from 2 mL/min to 10 mL/min process, the etching rate increases but decreased a little at 8 mL/min.There are no big changes on surface roughness, can be at 1.8 nm or less.