We propose a novel scheme to form a controllable eight-well optical trap for cold atoms or molecules by using an optical system of a binary π-phase plate and a lens illuminated by a plane light wave. We calculate the intensity distribution of the eight-well optical trap and the characteristic parameters of the eight-well trap (including geometric parameters, the intensity distribution, intensity gradients, and their curvatures), and discuss the evolution process of the optical trap from eight-well to four-well or from eight-well to double-well. The result shows that the proposed eight-well trap can be continuously changed into a four-well or double-well trap by moving the π-phase plate. We discuss the controllable optical lattice of eight-well which comes from combination of binary π-phase plate illuminated by single light beam and the rectangle lens combined system.