Ventilation device convenient to disassemble and assemble

The ventilation device comprises an outer installation cylinder embedded in the top of an elevator car, an inner installation cylinder is arranged in the outer installation cylinder, a lifting positioning assembly is arranged between the outer installation cylinder and the inner installation cylinder, a ventilation pipe is arranged on the inner wall of the inner installation cylinder, a dust filtering net is embedded in the top of the ventilation pipe, and a ventilation pipe is arranged on the inner wall of the inner installation cylinder. A ventilation fan is arranged on the inner wall of the ventilation pipe, and the air outlet end of the ventilation fan faces downwards. According to the ventilation device convenient to disassemble and assemble, an inner mounting cylinder is pulled downwards through a grabbing groove, a limiting sliding rod can slide relative to a limiting sliding block, the inner mounting cylinder can be lowered, operation is convenient, the situation that an operator is injured by crushin