It is observed by scanning tunneling microscopy (STM) that the adsorbed Benzotriazole (BTA) on copper is long in shape and has an irregular rectangle. The growth of BTA on copper is in the form of polymeric chain and mainly in one dimension rather than two dimensions. The copper surface covered by BTA becomes flatter,smoother and the roughness was smaller than that of bare copper, so the corrosion is largely decreased. However,many grooves can be seen between BTA polymeric chains in which corrosion may exist to a degree.