To study the incoherent beam combination characteristics of fiber lasers, a beam combination model of a circular array of multiple fiber lasers was established, and effect of waist radius w0, wave-front distortion of unit beam and beam separation distance on the far field beam quality of incoherent and coherent combination was simulated and analyzed. In addition, the influence of axis parallelism of multiple laser beams on the incoherent beam combination effect was studied, and experimental verification was carried out. The results show that, when the beam separation distance is d0=2.8w0, the beam quality β factor of incoherent combination of multiple laser beams without wave-front distortion is equal to that of coherent combination. The beam separation distance d0 decreases when the wave-front phase of laser beam is distorted, and the influence of wave-front distortion on the incoherent combination is less than that on the coherent combination. With the increasing of the parallel error among multiple laser beams, the beam quality of incoherent combination becomes worse. And the better the beam quality of unit beam is, the higher the demand for the axis parallelism of multiple laser beams. This research can provide references for the design and analysis of beam combination system of fiber lasers.