In order to study the replacement technology of blast furnace top gas-tight box,the installation and maintenance process of the airtight box are discussed in detail,and the flatness of the furnace top flange is re-measured and calibrated.During testing;Detailed comparison of current changes under high and low speed rotation and tilting lifting of gears,And the actual tilting angle and display angle of the chute in the airtight box were analyzed,The results show that when the maximum flatness error is 2.5 mm,the flatness error in the range of 60° is 0~2 mm,and the inclination error is less than 0.5°,there is no influence on the installation and operation of the airtight box.And strong air tightness,cloth accurate.