The utility model relates to the technical field of boiler manholes. The utility model discloses a boiler manhole door connecting device. The boiler comprises a boiler body, a flange is fixed at a manhole of the boiler body; the flange is connected with a manhole door through a stud; two ends of each stud respectively extend out of the inner end of the outer edge of the flange close to the boilerbody and the outer end of the manhole door, one end of each stud close to the boiler body is fixed with the inner end of the outer edge of the flange, nuts are respectively fixedly mounted at two endsof each stud, and a thermal insulation layer is additionally mounted between the inner end of the outer edge of the flange and the boiler body. The manhole door disassembling and assembling device isreasonable and compact in structure and convenient to use, when the manhole door is disassembled and assembled, on one hand, a heat preservation layer does not need to be damaged, on the other hand,the manhole door can be disassembled and assembled only by disassembling and assembling nuts on the side of the manhole door, and therefore the working efficiency of disassembling and assembling the manhole door is improved.