The invention discloses a sealed cutoff device for a PVC protective grating. The sealed cutoff device comprises a workbench, wherein a cutting knife groove is formed in the workbench; a liftable cutting disc is arranged in the knife groove; a housing fixed on the workbench is arranged above the knife groove; an air suction hole is formed in the housing and in one side of an end part of the knife groove; the air suction hole is connected with an air suction pipe; compaction structures are arranged in the housing and at the two sides of the knife groove; openable access doors are formed in the housing and at the two sides of the compaction structures; material ports are mutually symmetrically formed in the two access doors; and a hairbrush bar structure is installed on each of the material ports. The structure disclosed by the invention realizes complete sealing of the PVC protective grating during cutting, prevents dust from polluting a workshop, collects dust, and achieves higher smoothness during cutting, thus improving product quality.