Propagation of coherent and incoherent combined laser beams in atmospheric turbulence is numerically calculated by using extended Huygens-Fresnel principle. With beam propagation factor (BPF), the influence of atmospheric turbulence on far-field beam quality of coherent and incoherent combined laser beams is evaluated quantitatively. The investigation reveals that the far-field coherent combining irradiance distribution have the multiple side-lobes pattern of non-Gaussian character while propagating in free space with weak turbulence, and it have the advantage of high peak intensity over the incoherent combining counterpart. With the coherence length decreasing, the far-field coherent combining irradiance distribution gradually evolves into the pattern of its incoherent combining counterpart. The quantitatively calculation shows that for laser arrays with different laser number or different laser wavelength, the coherent combined beam quality is no better than its incoherent combining counterpart when propagating in stronger turbulent atmosphere. The mathematical model and calculation result can offer a reference for choosing and evaluating different combining schemes.