Based on the coherent superposition principle of direct-transmited light with the Gaussian speckle field, and also with the Kirchhoff approximation, the speckle in the deep Fresnel diffraction region is investigated. Expressions of speckle field in the deep Fresnel diffraction region, and the probability density of intensity, and contrast are obtained. In the deep Fresnel diffraction region of different scattering distance the variation of speckles is simulated with the height distribution data of random scattering surface measured by atomic force microscopy, and the curves of these two statistic functions are drawn. Combining the theory with the simulation, characteristics of these two statistic functions, the effect of the fraction of the direct transmit light intensity as well as their variations with the scattering distance are discussed.