A new beam combining and aperture filling technique using conjugate Dammann grating is introduced to direct all the energy of a mutually coherent laser array to the far-field main lobe in theor. The design scheme of beam combination for one-and two-dimensional coherent laser arrays is demonstrated. An experiment using an idealized simulated laser array with a mask is performed,which verifies the proposed concept. Experimental results show that such a beam combination scheme is efficient technique for the high-brightness and high-power laser systems. This technique is based on the far-field diffraction theory. The relation between grating plane and array plane is Fourier transformation. The aperture size and power density of the combined beam can be conveniently changed. It is very significant for the development of compact,light weight,and high-quality laser systems.