In this paper, an experimental scheme of a controllable double-well optical trap for cold atoms (molecules) is briefly introduced, and the fabrication method of a binary π-phase plate and the experimental results to generate a controllable double-well optical trap are reported. In the experiment, we investigated the dependence of the double-well parameters (such as the spatial position of optical double-well, the spacing between the centers of two wells and the relative intensity distributions and so on) on the phase errors of the π-phase plate, and the change of double-well intensities resulting from errors in the engraving depth of the binary π-phase plate as well as the evolution of the optical trap from two wells to single one are studied both theoretically and experimentally. Experimental results consistent with theoretical prediction are obtained.