Based on the extended Huygens-Fresnel principle, the expressions for effective beam parameter, beam size, angle spread, the variance of the angle-of-arrival fluctuation, and average intensity of the Gaussian Schell-model beam propagating on the level path through atmospheric turbulence are derived with the cross spectral density function of the beam employed, and the numerical results of these characteristic variables are presented. The influences of coherent length, atmospheric refractive-index structure constant, propagation distance and the waist radius on these variables are discussed.