Abstract: An improved automatic actuation device for inflatable life-saving equipment which comprises a housing, a compressed gas cylinder, a piercing pin for piercing the seal cap of the gas cylinder to open it, a L-shaped lever for driving the piercing pin and an automatic actuation device which will automatically operate when submerged in water to actuate the lever, characterized in that the automatic actuation device can be readily fitted on the compressed gas cylinder of any kind of the conventional life-saving equipment and comprises an outer cylinder, an inner cylinder, an actuating spring being compressing received between two cylinders, a water-soluble paper coil being surrounded around two projecting pins of the cylinders when two cylinders are pressed and fastened together and the water-soluble paper coil is used in the form of a replaceable unit.