Waterproof and dedusting negative pressure fan

The utility model discloses a waterproof and dedusting negative pressure fan which comprises a negative pressure fan body and further comprises a first shell, a second shell, a filter screen, a driving mechanism and shielding blocks. The negative pressure fan body is arranged in the first shell; the second shell is detachably arranged on the first shell, and the second shell and the first shell form a closed space; a through hole corresponding to the negative pressure fan body is formed in the second shell; a filter screen is detachably arranged at the through hole; each shielding block can be driven by a driving mechanism to move in the radial direction along the through hole of the second shell so as to control opening and closing of the through hole. When the shielding blocks abut against each other, a circle is formed, and the through hole is closed. A cleaning assembly is arranged below each shielding block; the lower end face of each cleaning assembly abuts against the filter screen. The utility model i