A method for preventing a baby falling down from bed to ground by use of an air cushion instead of conventional mattress is disclosed. Said air cushion is composed of a main body with flexible wall, a power supply with switch, a sound generator, and a pressure switch which can make the sound generator to generate sound when the internal pressure of air cushion is decreased or not to generate sound when increased. When a baby is separated from the air cushion, its internal pressure is decreased and alarm sound is generated. |