Abstract: The evolution of the water film in saturated sands and the responses of pore water and skeleton are investigated. It is shown that if the sand layer loses its strength and is not choked, there is no stable water film. If the choking state may keep, the water film may expand gradually, otherwise, water film will expand first and then enclose. Pore water's velocity, grain's velocity and pore pressure have discontinues at the first stage of choking. Discontinues will disappear with the disappearing of choking state.