Based on the formula of beam width of Gaussian-Schell model beam in strong turbulence, the expression of wander variance for a horizontal-path propagating partially coherent beam in the atmospheric turbulence is derived using the general expressions of the beam wander variance models of Andrews and Philips, and the spreading and wander of a partially coherent beam through the whole atmospheric turbulence are discussed. The results show that the partially coherent beam is less affected by turbulence than the fully coherent beam. The smaller the initial beam radius of partially coherent beam is, the more seriously the beam may be affected by turbulence. Within the short propagation distance, the beam wander caused by different wavelengths has little difference, which can reduce as the initial beam radius increases. When the propagation distance is further than 2 km, beam wander in both strong and weak turbulences is related to the wavelength, which is more obvious in strong turbulence. When the spatial coherence length is greater than 0.005 m, it has little effect on the beam wander in propagation distance of 10 km.