To analyze the corrosive inhibition effects of BTA in phosphoric slurry for copper electrochemical mechanical polishing(ECMP), the electrochemical behavior of copper in 30％ H₃PO₄ electrolyte with 0.01 mol/L benzotriazole (BTA) as an inhibitor was studied. The potentiodynamic polarization curves and the potentiostatic etching at different anodic potential of copper in the electrolyte were measured. The morphologies of the corroded workpieces were observed and the forming process of CuBTA surface film was analyzed by AFM and XPS. The results show that the surface roughness increases first with the dissolution of copper at a definite anodic potential range, then stabilizes at certain lower value owing to the dissolution inhibition effect of the Cu-BTA layer formed by adsorption of copper ions to BTA molecules. The anodic potential applied on copper should be kept below 0.5 V to sustain CuBTA film-formation, which takes near 2 min to stabilize at the test conditions.