In order to study the effect of additives on material removal rate of GaN chemical mechanical polishing（CMP）,the electrochemical etching of n-type GaN wafer was carried out by DC power supply.The effect of terephthalic acid(PTA) and hydrogen peroxide(H2O2) on material removal in CMP of GaN wafer were studied by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM).The results show that with addition of current,the removal rate of GaN material is first increased and then decreases with the increase of volume fraction of H2O2.In addition,the effect of PTA on the removal rate of GaN shows the similar trends as that of H2O2.When the volume fraction of H2O2 is 4% and the concentration of is PTA 10 mmol/L,the removal rate of CMP material of GaN wafer is the highest,which is 693.77 nm/h,and the surface roughness of polished Gan wafer is 0.674 nm.XPS analysis shows that the content of Ga2O3 on the surface of GaN wafer is increased after electrical induction,which indicates that the current promotes the oxidation and corrosion of GaN surface,thus improving the material removal rate