The optimal condition of bacteriorhodopsin (bR) adsorption onto the modified self-assembled monolayers (SAMs) was investigated. The SAMs of 11-mercaptoundecanoic acid (11-MUA) on the pre-treated gold substrate were used as a template, and modified with poly-l-lysine (PL) For the effective adsorption of bR. Based on the photoelectric responses of the bR thin films, it could be found that the optimal bR suspension concentration and buffer pH for bR thin film fabrication were determined as 5 mg/mL and pH 8, respectively.