The electrochemical impedance spectroscopy (EIS) technique has been used to investigate the feasibility of urea–hydrogen peroxide (urea–H2O2) slurries in copper chemical mechanical polishing (Cu CMP). The performance of the inhibiting-type and the chelating-type additives, BTA and NH4OH, were also explored. In order to analyze the surface-reaction characteristics of Cu, the equivalent circuit of double capacitor mode was mainly used to simulate the corrosion behaviors of Cu CMP in various slurries. In addition, via measuring dc potentiodynamic curves and open circuit potential (OCP), the corrosion characteristics were obtained in various slurries. Both EIS and AFM experimental results indicate that the slurry composed of 5 wt.% urea–H2O2+0.1 wt.% BTA+1 wt.% NH4OH can achieve the better Cu CMP performance. Its rms-roughness (Rq) after CMP and the removal rate (RR) attain to 2.636 nm and 552.49 nm/min, respectively.