A method for making a lens barrel includes the steps of: (a) forming a fusible mold core having at least one flange; (b) applying an insulating layer on the fusible mold core; (c) disposing the fusible mold core in a lens-barrel-forming mold; (d) feeding a molding material into the lens-barrel-forming mold to form the lens barrel between the lens-barrel-forming mold and the fusible mold core and adhered to the fusible mold core, the lens barrel having at least one inner cam groove corresponding to the flange of the fusible mold core; (e) removing the lens barrel together with the fusible mold core from the lens-barrel-forming mold; and (f) fusing the fusible mold core for separating the fusible mold core from the lens barrel.