A technique for simultaneous beam combination and aperture filling of a coherent laser array that uses a conjugate Dammann grating is proposed. It can convert light from a coherent laser array into a single-lobed far field with high quality. An experiment with a simulated 5x5 2D coherent laser array using an aperture mask has been performed. The feasibility of the proposed scheme is verified. It provides an important basis for achieving a high-power and high-brightness laser beam from an actual coherent laser array.