A sponge roller, a cleaning roller assembly, and a floor cleaner. The sponge roller includes an outer layer and an inner layer. The outer layer is sleeved on the inner layer; the inner layer is made of non-absorbent sponge, and the outer layer is made of absorbent sponge. The sponge roller can be made with a large thickness, thus improving the cleaning capacity of the cleaner. The water is mainly stored in the outer layer, so it can be squeezed out without the exertion of much more external force, and thus the resistance against the rotation of the sponge roller is negligible, thus saving the energy consumption.