A kind of sterilization method Medical Instruments is connected to reservoir using a vacuum cavity, by valve closing state, it discloses including placing instrument in non-aseptic state to sterilization battery pack, opens chamber, make to be fitted into chamber, room is closed, the first air is taken out from room, changes a large amount of liquid waters and be converted to steam, valve is opened, it introduces bactericidal agent and enters chamber, the second volume of air is introduced into the chamber, opens the room, packet is removed from the chamber, removes instruments sterility from battery pack. This method may further include the following steps: determine the indoor pressure of chamber repeatedly, the pressure of second derivative values is calculated relative to the time, be present in corresponding value with any one piece of second dervative local maximum of determination, pressure be higher than and/or lower than triple point pressure water.
