The invention discloses a method for reducing micro water in a sulfur hexafluoride steel cylinder. The method comprises the following steps: a special sulfur hexafluoride steel cylinder is prepared, and nitrogen is filled in the cylinder for the first time; the nitrogen filled in the special sulfur hexafluoride steel cylinder for the first time is pumped, and the nitrogen is filled in the cylinder for the second time; the nitrogen filled in the special sulfur hexafluoride steel cylinder for the second time is pumped, the nitrogen is filled in the cylinder for the third time, and the nitrogen filled in the steel cylinder for the third time is pumped; the surface temperature of the steel cylinder is kept at 75 DEG C by using a heater; the steel cylinder heater is withdrawn, a vacuumizing device is immediately used for extracting the nitrogen for replacing the micro water in the steel cylinder, and -3 MPa atmospheric pressure in the empty steel cylinder is kept more than 30 minutes; and qualified sulfur hexafluoride gas and liquid are filled in the steel cylinder. The method has such advantages as convenient for operation, low investment and high product yield, satisfies the demands in the sulfur hexafluoride steel cylinder filling industry, can prominently improve the steel cylinder use pass percent, and is excellent in popularization value and application prospect.