First-and second-order statistical properties of ultrasonic speckles reflected from a rough interface are studied theoretically and experimentally in this paper. A theoretical model for predicting statistical properties of ultrasonic speckles is constructed, based on the Fresnel-Huygens principle and three basic assumptions. Distributions of the amplitude and phase of ultrasonic speckles in a scattering space are studied; the study shows that they are in the form of Rayleigh and uniform distribution, respectively. Using the proposed model, the average transverse size of the speckles within a scattering domain, which are received by a focus probe, is investigated. The average transverse size is found to be dependent on the characteristics of the measuring system only, and does not vary with the position in the domain. To verify the applicability of the theoretical model, a special experimental set-up was designed. The corresponding experiments were conducted for measuring the sound pressure of the ultrasonic speckles reflected from a rough interface between water and aluminium alloy. The numerical results are compared with the experimental ones. The comparison demonstrates that the theoretical model and the three related assumptions are suitable for analysing statistical properties of ultrasonic speckles reflected from a rough interface.