Quantitative details about coherence are important for determining the performance of laser arrays. In this paper，we deduce the analytical equation of the far-field intensity distribution in partially coherent combining of fiber laser arrays and investigate its effects on the far-field patterns, the FWHM of the central far-field lobe, strehl ratio and power in the bucket. The master oscillator-power amplifier scheme was used to realize phase control of three ytterbium fiber amplifiers, and the experimental results are presented.