In this paper, an experimental and theoretical investigation on finite-amplitude reflection sound wave of circular piston sources is presented. The reflected field of harmonic waves from the boundary surface have been calculated. Thinking of them as the waves which radiate from the image of the piston source and treating them as the waves that seem to be generated by a new source on the vibrating boundary surface, by means of weak-shock theory, the reflection of the finite-amplitude waves can be predicated.By making use of the boundary wall of a pool, some experiments on second harmonic reflection have been done. It is shown that the average attenuation of the harmonic pressure with distance is consistent with the theory. However, along the longitudinal distance and in the cross sections perpendicular to it there are obvious interference of the harmonic waves, and longitudinal interference lengths have an order of magnitude greater than the traverse ones. According to the theoretical evaluation, it seems to be that the reflection results from the pool wall that has a thickness, a small angle between its two boundary surfaces and a fixed beam width of the primary wave. The theoretical evaluation and the experiments are in agreement with each other.