In this paper, according to the analytical equation of the far-field intensity distribution in coherent combination of fiber laser arrays, we investigate the influence of fill factor of the laser arrays, elements and phase errors on the far-field patterns, the energy and angular width of the main lobe. At last, we describe the experimental study of the coherent combining of three-element fiber-laser arrays based on ytterbium polarization-maintaining single-mode power amplifiers with the fill factor of 12.5%.