Self-Assembled Monolayer (SAM) is method for increase corrosion protection efficiency of metal surface that widely used in heat exchanger. The method for prepare metal surface before coating have an affect on adsorption of coating solution which increase efficiency of corrosion protection. Therefore, this context studied optimum method for preparation copper surface before coating with octadecanthiol (ODT) for corrosion protection in heat exchanger such as polished surface with emery paper only, used oxygen plasma, immersed in piranha solution (sulfuric acid + hydrogen peroxide), immersed in nitric acid, immersed in hydrogen peroxide, immersed in hydrogen peroxide and nitric acid, immersed in hydrochloric acid, and immersed in phosphoric acid. The ODT SAM on copper surface was characterized by contact angle measurements, Scanning Electron Microscope (SEM) and Atomic Force Microscopic (AFM). Corrosion protection ability of ODT SAM was evaluated in aqueous NaCl solution using potentiodynamic polarization. Results showed evidence that, the optimum condition of copper surface treatment for ODT SAM coating for corrosion protection was oxygen plasma treatment at -400 mmHg from ambient pressure for 20 minute