The utility model relates to a sealing device, concretely relates to dry gas seal for ammonia compressor, including the spring holder, quiet ring, rotating ring and axle sleeve, the spring holder is docked each other by spring holder A and spring holder B and constitutes, quiet ring includes that quiet ring A and quiet ring B and the two branch locate the both ends of rotating ring, all be equipped with resilient means between quiet ring A and the spring holder A and between quiet ring B and the spring holder B, be equipped with the rand between this spring holder and the quiet ring, still include sealed ring spring, axial closing device, the locating plate, the rotating ring passes through the connection terminal surface of sealed ring spring coaxial arrangement at the axle sleeve, still be equipped with the trundle between rotating ring and the axle sleeve, axial closing device locates between spring holder B and the axle sleeve, the one end of locating plate is inserted in the socket of locating the axle sleeve outer wall, the other end passes through screw and spring holder B fixed connection, adopt the utility model discloses it is strong that technical scheme's dry gas seal for ammonia compressor has the suitability, and sealing performance well and convenient operation's characteristics.