The utility model discloses a coupling mechanism for between gas cylinder and syringe, coupling mechanism including the double thread pipe that admits air that connects gradually, interior screwed joint, the double thread of giving vent to anger pipe and threaded connection in that gives vent to anger double thread pipe end portion gets the gas head, the intraductal flexible socket joint of the double thread that admits air there is the intake pipe, the intraductal flexible socket joint of the double thread of giving vent to anger there is the outlet duct, just the syringe locator is fixed set up in get in a fit of anger, the syringe locator with still be provided with the sealing plug between the outlet duct, just syringe is provided with the crack on the sealing plug so that can run through in proper order the syringe locator with the crack extends to gas is got to the outlet duct, the double thread pipe that admits air is kept away from interior screwed joint's one end is connected in the relief pressure valve of gas cylinder. Coupling mechanism can make and reduce gaseously extravagant getting the gas in -process, and this coupling mechanism structure is simple, convenient to use, easily installation.