Based on the quadratic approximation of the Rytov’s phase structure function and the Huygens-Fresnel principle, propagation equation for the spatial degree of coherence of partially coherent flat-topped beams propagating in turbulence atmosphere is derived, and the properties of the spatial degree of coherence in turbulence atmosphere are investigated numerically. The result shows that properties of spatial degree of coherence of partially coherent flat-topped beams are determined by the refractive index structure constant of atmospheric turbulence, the beams’ relative length of the space-related, the order of flat-topped beams, transmission distance and location of the observation point in common. It also shows that the oscillatory behavior and phase singularities of the spatial degree of coherence may occur when partially coherent flat-topped beams propagates through atmosphere turbulence. But the oscillatory behavior becomes sweaker with atmosphere turbulence increasing, and the phenomena of the oscillatory behavior and phase singularities will disappear in the end.